Unusual Chapter Numbers

"Chapters in books are usually given the cardinal numbers 1, 2, 3, 4, 5, 6 and so on. But I have decided to give my chapters prime numbers 2, 3, 5, 7, 11, 13 and so on because I like prime numbers."

- The Curious Incident of the Dog in the Night-Time

Doing odd -- no, peculiar things with your chapter numbers. Which can be either odd or even. Or fractional. Or even stranger things, up to and including non-numeric. Representing them with formulas or other non-standard formats works, too.

Compare Idiosyncratic Episode Naming, Episode Zero the Beginning.

Anime and Manga

 * Flashback chapters in Bleach uses negative chapter numbers relative to how far back from the beginning they are. Toshiro Hitsugaya's special chapter is -15, while the Turn Back the Pendulum arc consists of chapters 108 to -97. A chapter about how Mizuiro and Keigo became friends with Ichigo and Chad was numbered .8 and two about events immediately before the beginning of the story were numbered "0.side a" and "0.side b".
 * A special chapter tying in with one of the movies is called Imaginary Number 1.
 * School Rumble plot chapters are labeled #1, #2 and so on, but chapters about minor characters are labeled with â™­. There are also a few 'natural' chapters.
 * Nana has a book of extra episodes numbered "7.8": this is both a joke on the two protagonists' names (Nana = 7 and Hachi = 8 in japanese) and a way to say it is meant to be read after volume 7 and before volume 8, it spite of this being published some time after these.
 * Invoked in ADV Films' dub of Neon Genesis Evangelion; the tapes were referred to as "Genesis 0:1", "Genesis 0:2", etc. up to "Genesis 0:13".
 * Recap episodes of Code Geass were numbered (number of the previous episode).5 with the next episode continuing onto the next whole number.
 * Which is also the case for some other animes with recap episode (i.e. Legend Of Legendary Heroes)
 * The Saiyuki main-story series (Gensomaden, Reload, and Blast) have chapters organized into numbered "acts"--roughly equivalent to plot arcs. There are fractional numbered acts for omakes, and full-chapter flashbacks are listed as "act.xx".

Comic Books

 * The comic book Milk and Cheese's first five issues were numbered #1, Other #1, Third #1, Fourth #1, and "First Second Issue."
 * Zero Hour numbered the main storyline backward because it was counting down to... Zero Hour. Various titles in The DCU have tie-in issues numbered #0; most significantly, the issues of Legion of Super-Heroes and Legionnaires that began the Legion's first full-fledged Re Boot.
 * Countdown to Final Crisis did the same thing, counting backwards from 52.
 * This happens occasionally in long running comics that have been restarted various times. Via loopholes in how volumes are decided the editors can shuffle the numbers around to celebrate milestones. For example Thor #28 of the most recent volume will be/was numbered as Thor #600. Naturally this can be very very confusing, especially when the numbering is reset multiple times in relatively short order.
 * DC One Million saw every DCU title jump to #1,000,000 for an issue as the far future DCU interacted with the present day.
 * Groo the Wanderer has had at least three "#1" issues (because it changed publishers, and because "#1" sells better). Original author Sergio Aragon Ã©s claimed that every issue he wrote was #1.
 * In a similar manner to DC's "zero issues", which were Flashbacks to origin stories, Marvel had a Fifth Week Event of stories set before the characters' origins (Peter Parker as a kid; mutants before the founding of the X-Men, etc), numbered "#-1".
 * Long after both events, Booster Gold had a Zero issue (tying into Zero Hour and restating his origin) and a One Million issue (introducing Booster's 1M counterpart, Peter Platinum).
 * Given all this, it's almost not unusual that the Earth X trilogy featured the first issue as "0", the second through thirteenth as "1-12", and the last as "X". (With a number of titled but un-numbered comics in between during the runs of Universe and Paradise X.
 * In 1999, the publisher of ~2000 AD~ decided to stop doing annuals in favour of triple-length December issues, which are cheaper and sell better. Each of these special issues has been given the number of the next year, starting with December 1999's 'prog 2000' and continuing through prog 2001 (December 2000), prog 2002 (December 2001), etc. Naturally, the number of the first issue of January directly follows that of the last issue of November, but the stories in the December issue still fall between them. One wonders what will happen when it actually reaches issue 2000.
 * Marvel now have "Point One" issues, standalone stories that establish the characters' status quo, published as, for example, #37.5 (between #s 37 and 38). Intended as a jumping on point, it might work better if any care was made to ensure that #38 isn't part four of a six-part story.
 * Like Zero Hour above the miniseries Marvel: The Lost Generation the numbering go backwards matching the timetravelling POV character.
 * Back before it ended, the Deadpool Team Up series was numbered backwards, starting at 1000.
 * The Recent Venom Arc, the circle of four, got the numbers 13.1 through to 13.5. 13 itself had nothing to do with the arc.

Fanfic

 * Starkits Prophecy is more than a little careless with its chapter numbers. Whether or not numbers are being skipped or duplicated, they are frequently subjected to Rouge Angles of Satin when spelled out.

Literature
"Mike: This edition seems to have omitted Chapter Pi."
 * In Logan's Run, the chapter numbers go down.
 * Similarly, the section numbers in Everything Matters count down to the destruction of life on earth.
 * In Dan Abnett's Warhammer 40000 novel Titanicus, the chapter numbers are in binary.
 * In Margaret Ball's Mathemagics, the chapter numbers are mathematical formulae that can be solved for the actual number. (She lists the solutions in the back.)
 * The Curious Incident of the Dog in the Night-Time only has prime-numbered chapters, due to the narrator disliking other numbers.
 * Storm, by George R. Stewart is chaptered "The First Day", "The Second Day", "The Third Day" and so on. There are no chapter numbers.
 * The Name of the Rose does the same thing, and subdivides the chapters according to the hours of the monastic day.
 * Wayside School Is Falling Down is stuck on the nineteenth story for three chapters. The following chapter is headed "20, 21 & 22: Eric, Eric and Eric".
 * The previous book, "Sideways Stories from Wayside School," has no Nineteenth chapter at all (since the school isn't supposed to have a nineteenth story, either.) Instead, between chapters 18 and 20 we get a notice saying "there is no nineteenth story. Sorry."
 * The Gods Themselves by Isaac Asimov starts with chapter 6 of its first section, before flashing back to chapters 1-5 (i.e. the story is told out of order but the chapters are numbered in strict chronological order).
 * It also breaks all the chapters in the second section of the book into three parts, numbered 1a, 1b, 1c (all of the action in these chapters are taking place at roughly the same time), 2a, and so on; the letters correspond to three different viewpoint characters.
 * The three books in Robert Anton Wilson's Schrodinger's Cat Trilogy are all Book One, and the parts of each book are all Part One.
 * In Alcatraz Verses the Evil Librarians book four, due to its offbeat style, the book starts on chapter 2, then skips to chapter 6 (mentioning how boring chapters 3-5 were) from there it proceeds to chapter pi, then 4 1/2, then 42. Eventually you read through Act V, scene III, Chapter No!, Chapter 24601 (a reference to Les Misérables), Chapter 8675309, Chapter Infinity, and chapter infinity plus one, along with many other crazy chapter titles.
 * The Eye of Argon includes a Chapter 3 1/2 and a Chapter 7 1/2.


 * The Running Man also does a countdown. Appropriate, since the main character has to survive for a specific time to win a prize..
 * Life in the Fat Lane's chapters are numbered according to the weight of the protagonist.
 * The Ring of Ritornel counts up to chapter 12, then starts counting down again; each chapter in the second half has a title which is a variation on the previous chapter with the same number. The final chapter in numbered x.
 * How To Eat Fried Worms has a chapter-and-a-half, and one chapter literally has only a blob of ink for a chapter name and number. (It's sometimes referred to as "Chapter Splort" in readings.)
 * The chapters in Jurassic Park are titled "First Iteration", "Second Iteration", etc., in keeping with Ian Malcolm's interest in fractals (and the actual fractals are shown). In The Lost World, it becomes "First Configuration", "Second Configuration" etc.
 * The iteration count is wrong - the "first iteration" actually is the third and so on. (This might be because the first and second iterations don't look very interesting)
 * Going Postal, the first non-young-adult Discworld novel since The Colour of Magic to feature chapters, has a chapter 7A instead of a chapter 8 (because the number 8 is considered unlucky on the Discworld).
 * And while Thief of Time (as stated above) does not have chapters or chapter numbers, it does have a "tick" in the middle of each break in the text... at least until it doesn't
 * The chapters of I Am the Messenger are all playing cards, as each of it's four acts begin with the main character receiving an Ace of each of the suits.
 * The Man Who Loved Only Numbers, a biography of Paul Erdos, starts with chapter 0, then goes up through one, two, e, three, pi and so on, before ending with an epilogue: Chapter Infinity.
 * Aside from the prologue, each chapter of A Night in the Lonesome October by Roger Zelazny is titled October 1, October 2, etc., all the way to October 31, as each chronicles the events of that day.
 * All the chapters in Zelazny's Roadmarks are numbered either "One" or "Two," indicating separate plot threads.
 * In Roddy Doyle's book, The Giggler Treatment, there were a few flashback chapters. The narrator apparently lost track of what chapter he was on after those and began naming chapters things like, "The Chapter After That Last One", "Chapter Mammy Doyle" and "This Chapter Is Named After Elvis Presley Because He Lives Under The Shed In Our Back Garden."
 * Not forgetting "Chapter Something"!
 * The Captive by Scott O'Dell uses Mayan numerals for chapter numbers.
 * In Survivor by Chuck Palahniuk, the chapter numbers count down, as do the page numbers.
 * The Doctor Who Expanded Universe novels are full of this. There has been at least one instance of numbers counting down. It almost always has something to do with Time Travel.
 * The Torchwood novel The Men Who Sold The World has six Chapter Nineteens, each (except the last one) ending with . It also has flashback chapters headed "X Years/Months/Weeks Earlier..." and a prologue and epilogue headed "100,000 BC"
 * In John Varley's time travel novel Mammoth, the chapters are numbered in absolute chronological order, which is not the order the story is told in.
 * Iain M. Banks's Use of Weapons has two interleaved streams of chapters, one conventionally numbered in sequential Arabic figures for the main story set in the Present, and one counting backwards in Roman numerals working through the protagonist's backstory.
 * Tik Tok has twenty-six chapters, which don't have numbers, but each one begins with the appropriate letter of the alphabet in a very large font. (So chapter one begins "As I look..", chapter two begins "Broaching the second chapter..." and so on. The writer has to cheat a little: for example, chapter four has "Hey Dummy!" and chapter seventeen has "Q. Cue the bloody rainbow...")
 * The Neverending Story does the same thing.
 * Family Bites by Lisa Williams has "Chapter Twenty-Four - Part One" and "Chapter Twenty-Four - Part Two".
 * Imzadi, a Star Trek: The Next Generation novel by Peter David, doesn't have chapter numbers, but it has section titles such as "The End", "The Beginning of the End", "Interlude", and "The End of the Beginning". Though thematically appropriate for the sections, and entirely understandable for a time travel novel, they have nothing to do with their locations in the book.
 * In the Greek version of The Bible, the Septuagint, the Book of Esther has additions not found in the Hebrew versions. They were numbered to come after the rest of the book, but later re-inserted into more appropriate places. Consequently, the chapter numbers are out of order, and the book actually begins with Chapter 11.
 * Alain Damasio's La Horde du contre-vent has reverse numbered pages. It can be startling if you only notice it halfway through the book.
 * Georges Perec's La disparition (translated into English as A Void) is a lipogram - the letter E never appears in the text. It's 26 chapters long, but chapter 5 is missing.
 * Atlanta Nights has two chapters called Chapter 12 and no chapter 21. There's no real reason behind it, other than adding to the overall lack of professionalism in the book.
 * The Thursday Next books begin every chapter on a right-hand page. If the previous chapter ends on a right-hand page, the intervening left-hand page is blank. There is no Chapter 13, although one is listed in the contents -- with the page number of the blank page before Chapter 14.
 * The book The Dancing Wu Li Masters (Think Zen and the Art of Motorcycle Maintenance) numbered each chapter "Chapter One," with a different title under each one. The philosophy behind this is eventually explained in the book.
 * Looking for Alaska is separated into two sections, Before and After. Each section is divided into days (like 10 days before or 75 days after), with Before counting up to  and After wrapping everything up.
 * A few Captain Underpants books have chapters numbered X 1/2, and one even has one with a 3/4.
 * The Otto Undercover series by Rhea Perlman does this a lot. For example, in the first book, the table of contents lists "Chapter Minus 1", "Chapter 0", "Chapter Regular 1", "Too Many Chapters", and "The End". The actual names of the chapters in the book are "Chapter Minus 1", "Chapter 0", "Chapter Regular 1", "Chapter 2", "Chapter 2½", "Chapter 3", "Chapter 4", "Rude Interruption of the Story, Number One", "Chapter 4 Again", "Rude Interruption of the Story, Number Two", and so on...

Live Action TV

 * Mystery Science Theater 3000 began as a local TV show (on Minneapolis station KTMA), then became a 10-year national series on The Comedy Channel (later Comedy Central) and then the Sci-Fi Channel. Since all of its cable-era marketing treated the first national season as Season 1, fans and show archivists retroactively "numbered" the KTMA episodes "K01" through "K21", with an unaired pilot-show fragment numbered "K00". Confusingly, IMDb originally called the KTMA shows "Season 0", but has now renumbered them all to Seasons 1-11, breaking with all other information sources (but oddly keeping the "0" number for the "pilot").
 * QI labels its seasons not with numbers but with letters, with series 1 being called "Series A", series 2 being "Series B" and so on.

Music

 * Professor Peter Schickele (University of Southern North Dakota at Hoople) is the world expert on the music of P.D.Q. Bach - the last and certainly least of Johann Sebastian Bach's sons. He has assigned Schickele numbers (S) to PDQ Bach's works.
 * The 1712 Overture is S. 1712.
 * The Classical Rap is S. 1-2-3
 * Einstein on the Fritz is S. e=mc2
 * The Erotica Variations is S. 36EEE
 *  Hansel and Gretel and Ted and Alice (an opera in one un-natural act) is S.2n-1 (odd!)
 * The 'Howdy' Symphony is S. 6 7/8

Tabletop Games

 * The Malkavian clanbook in Vampire: The Masquerade. So much so it calls the Appendixes "Liver One" and "Kidney Two".
 * The Normality game master's guide, which only manages to be a little less weird and disturbing than the other book. And that's very, very weird and disturbing.

Video Games

 * There are franchises beyond count in which the numbers in the title have no actual bearing on the title's chronological place in the series. For example, Grand Theft Auto starts with GTA 1, then GTA 2, then GTA 3. So far, so good. Then comes Grand Theft Auto: Vice City. Then San Andreas. Followed by the sixth game in the franchise, Grant Theft Auto IV.
 * Braid began with World 2 and works it way to World 6, with World 1 being the last world you visit. It could be symbolic of the fact that
 * Similarly, the stages in World 1 count down from 4 to 1, probably for the same reason.
 * The stages in Radiant Silvergun are numbered not by the order they're played by, but by the time period they take place. Because of this, the final stage, which is set millions of years in the past, is Stage 1.
 * The story of The World Ends With You is played by week. During the first week, each day starts with a "THE XTH DAY" screen and ends with a "CHAPTER TITLE" screen. The second week starts over, so your eighth day is again "THE 1ST DAY", ninth is "THE 2ND DAY" and so on. The first day of the third week, however, is The unlockable bonus chapter is "ANOTHER DAY".
 * The version of Free Cell that comes with Windows has either 32,000 (pre-XP) or one million games, which are given positive numbers starting from 1. However, there are also secret deals -1 and -2, which are impossible. Vista added deals -3 and -4, which are quite the opposite.
 * Minecraft Alpha and Beta releases had version numbers in the format of 1._____, eventually culminating in 1.9 prerelease 5. The "final" version of Minecraft is simply numbered version 1.0.0.
 * The arcade game Kamen Rider Battle: Ganbaride used straight numbers for its first several sets. When Kamen Rider OOO premiered, the sets were relaunched with set 001, and when Kamen Rider Fourze premiered it was relaunched again with set 01. The same thing happens with Super Sentai Battle: Dice-O, where the early sets just had numbers, the Kaizoku Sentai Gokaiger sets used "DX-{number)", and the Tokumei Sentai Gobusters sets used "Tokumei-(number)".
 * Touhou uses fraction for in-between installments. 7.5, 10.5, and 12.3 were fighting games, 9.5 and 12.5 were unique photographing games, 12.8 was a Lower Deck Episode with Cirno as the main character. (Yes, there were 3 games between Touhou 12: Undefined Fantastic Object and Touhou 13: Ten Desires. No, they aren't examples of Capcom Sequel Stagnation.)

Webcomics

 * Adventurers had hundreds of strips numbered 999 during the final boss battle arc, as a joke on Caps in RPGs.
 * The two prequel books for Order of the Stick are numbered volume 0 and volume -1.

Web Original

 * "A Beginner's Guide To The British" has Part One, Part Two, Part Four three (oops), Part Four, and Part Four five.
 * The Nostalgia Critic, in his Top 11 Mind**** Countdown used entries such as "Number Guttenburg" "Number Lamp" and "Number Number" (depicted by a # sign).
 * The Book of Sand puzzle does this with PAGE numbers. The page numbers are 999, 1001, 40514, 82499, 71077345, 3141592654, 11111000101, and 23^9. Worse yet, they don't take place in order. Rather, the reader has to put them in order based on context of the story.

Non Fiction
""Since all other reference manuals have Appendices, it was decided that the INTERCAL manual should contain some other type of removable organ.""
 * One should not be surprised to open up a programming language reference book and see that the chapter numbers start at zero. If the author of the book has done this, the language will almost certainly use zero as the index of the first item in an array. Probably the languages to get this treatment the most are C and C++.
 * Some math books also do this.
 * John Conway's On Numbers and Games not only starts at chapter zero, it's also divided into a "zeroth part" and a "first part."
 * The INTERCAL reference manual has a tonsil instead of an appendix.


 * Similarly, one strategy guide for the computer game Monty Python's Complete Waste of Time includes spleens instead of appendices, and they're scattered throughout the book rather than all placed at the end. Most of these are just quotes from various Monty Python sketches that are vaguely relevant to that part of the game.
 * Donald Knuth has a tendency to give his software idiosyncratic version numbers. The release versions of his font-design program METAFONT are 2, 2.7, 2.71, 2.718, etc, asymptotically leading to the constant "e"; similarly, the release versions of his typesetting program TeX are 3, 3.1, 3.14, and so on, converging to "pi".
 * It's been joked (possibly by Knuth himself) that when he dies the version numbers will be changed to e and pi respectively, and any further bugs will thereby be considered features.
 * That's no joke. He really wants people to do that when he dies.