# 42 (number)

42 (forty-two) is the natural number that follows 41 and precedes 43.

## Mathematics

42 is a pronic number, an abundant number as well as a highly abundant number, a practical number, an admirable number, and a Catalan number.
The 42-sided tetracontadigon is the largest such regular polygon that can only tile a vertex alongside other regular polygons, without tiling the plane.
42 is the magic constant of the smallest non-trivial magic cube, a $3\times 3\times 3$ cube with entries of 1 through 27, where every row, column, corridor, and diagonal passing through the center sums to forty-two.
42 can be expressed as the sum of three cubes:$80,435,758,145,817,515^{3}+12,602,123,297,335,631^{3}+(-80,538,738,812,075,974)^{3}=42.$

## Technology

* Magic numbers used by programmers:
** In TIFF (Tag Image File Format), the second 16-bit word of every file is 42, "an arbitrary but carefully chosen number that further identifies the file as a TIFF file".
** In the reiser4 file system, 42 is the inode number of the root directory.
** In the military IRIG 106 Chapter 10 data recording standard, the hex value 0x464F52545974776F (ASCII "FORTYtwo") is used as a magic number to identify directory blocks.
** The GNU C Library, a set of standard routines available for use in computer programming, contains a function—memfrob—which performs an XOR combination of a given variable and the binary pattern 00101010 (42) as an XOR cipher.
** The password expiration policy for a Microsoft Windows domain defaults to 42 days.

## Wisdom Literature, Religion and Philosophy

* Abrahamic religions
** In Judaism, by some traditions the Torah scroll is written with no fewer than 42 lines per column, based on the journeys of Israel. In the present day, 42 lines is the most common standard, but various traditions remain in use (see Sefer Torah).
** 42 is the number with which God creates the Universe in Kabbalistic tradition. In Kabbalah, the most significant name is that of the En Sof (also known as "Ein Sof", "Infinite" or "Endless"), who is above the Sefirot (sometimes spelled "Sephirot"). The Forty-Two-Lettered Name contains four combined names which are spelled in Hebrew letters (spelled in letters = 42 letters), which is the name of Azilut (or "Atziluth" "Emanation"). While there are obvious links between the Forty-Two Lettered Name of the Babylonian Talmud and the Kabbalah's Forty-Two Lettered Name, they are probably not identical because of the Kabbalah's emphasis on numbers. The Kabbalah also contains a Forty-Five Lettered Name and a Seventy-Two Lettered Name. 42 letters make the Ana beKo'ach prayer.

## Popular culture
### The Hitchhiker's Guide to the Galaxy

The number 42 is, in The Hitchhiker's Guide to the Galaxy by Douglas Adams, the "Answer to the Ultimate Question of Life, the Universe, and Everything", calculated by an enormous supercomputer named Deep Thought over a period of 7.5 million years. Unfortunately, no one knows what the question is. Thus, to calculate the Ultimate Question, a special computer the size of a small planet was built from organic components and named "Earth". The Ultimate Question "What do you get when you multiply six by nine" is found by Arthur Dent and Ford Prefect in the second book of the series, The Restaurant at the End of the Universe. This appeared first in the radio play and later in the novelization of The Hitchhiker's Guide to the Galaxy.
The fourth book in the series, the novel So Long, and Thanks for All the Fish, contains 42 chapters. According to the novel Mostly Harmless, 42 is the street address of Stavromula Beta. In 1994, Adams created the 42 Puzzle, a game based on the number 42. Adams says he picked the number simply as a joke, with no deeper meaning.
Google also has a calculator easter egg when one searches "the answer to the ultimate question of life, the universe, and everything." Once typed (all in lowercase), the calculator answers with the number 42.

### Jackie Robinson

* The jersey number of Jackie Robinson, which is the only number retired by all Major League Baseball teams. Although the number was retired in 1997, Mariano Rivera of the New York Yankees, the last professional baseball player to wear number 42, continued to wear it until he retired at the end of the 2013 season. As of the 2014 season, no player ever again wore the number 42 in Major League Baseball except on Jackie Robinson Day (April 15), when all uniformed personnel (players, managers, coaches, and umpires) wear the number.
** 42 is a film on the life of American baseball player Jackie Robinson.
** Miles Morales was bitten by a spider bearing the number 42, causing him to become a Spider-Man. The number was later heavily referenced in the film Spider-Man: Into the Spider-Verse. The use of 42 within the franchise references Jackie Robinson's use of the number, though many fans incorrectly believed it to be a Hitchhiker's Guide to the Galaxy reference.

### Other

In Japanese culture, the number 42 is considered unlucky because the numerals when pronounced separately—shi ni (four two)—sound like the word "dying", like the Latin word "mori".
A sheet of A4 copy paper would require 42 half-folds in order to reach the Moon from the surface of Earth.