42 is the natural number following 41 and followed by 43.

Cardinal	forty-two
Ordinal	42nd (forty-second)
Factorization
Divisors	2, 3, 6, 7, 14, 21
Roman numeral	XLII
Binary	101010
Hexadecimal	2A

In mathematics

This composite number's factorization makes it a sphenic number. It is also the third 15-gonal number, a Catalan number, a meandric number, an open meandric number, a Harshad number and a self number. It is bracketed by twin primes.

In astronomy

• Messier object M42, a magnitude 5.0 diffuse nebula in the constellation Orion, also known as the Orion Nebula
• The New General Catalogue object NGC 42 , a spiral galaxy in the constellation Pegasus
• The Saros number of the solar eclipse series which began on 1577 BC April 28 and ended on 297 BC June 5. The duration of Saros series 42 was 1280.1 years, and it contained 72 solar eclipses.
• The Saros number of the lunar eclipse series which began on 1293 BC January 24 and ended on 59 April 15. The duration of Saros series 42 was 1352.2 years, and it contained 76 lunar eclipses.

In religion

• The number of men of Beth-azmaveth in the Census of men of Israel upon return from exile. (Holy Bible, Ezra 2:24)
• The number of months the Beast will hold dominion over the Earth. (Holy Bible, Revelation 13:5)
• The number of generations recorded between Abraham and Jesus in the Gospel of Matthew. (Holy Bible, Matthew 1:17)
• The maximum total number received of any one present in the song The Twelve Days of Christmas.
• There are 42 principles of Ma'at.

In other fields

Forty-two is also:

• The atomic number of molybdenum
• The answer to the Ultimate Question of Life, the Universe and Everything, according to Douglas Adams' book The Hitchhiker's Guide to the Galaxy.
• The age at which "The King" Elvis Presley (who appears in the Hitchhiker's Guide) died.
• In Lewis Carroll's book The Hunting of the Snark, (before Douglas Adams' book was written) the baker left 42 pieces of luggage on the pier. Lewis Carroll was strangely fascinated by this number. For more references, read The Annotated Alice.
• The sum of the numbers or spots on a pair of conventional (six-sided) dice.
• The second 16-bit word of every TIFF format image file, used together with the first word to indicate byte order.
• The name of a Texan trick-taking game played with dominoes (see 42 (dominoes)).
• The number of the French department Loire.
• The minimum age one had to have to be elected a consul in the Roman Republic.
• The jersey number of Jackie Robinson, which is retired by all Major League Baseball teams.
• The jersey number of Pat Tillman, which was retired on November 13, 2004 by Arizona State University.
• The number of distinct types of cheese requested in Monty Python's Cheese Shop sketch.
• Fox Mulder's apartment number - speculation would lead to a tip of the hat to The Hitchhiker's Guide To The Galaxy.
• One barrel of oil is equivalent to 42 gallons of oil.
• Wolves and dogs (Canines) have 42 teeth.
• The movement number of the Hallelujah Chorus in Handel's Messiah .
• Part of the name of:
  • 42 BELOW, a vodka produced in New Zealand.
  • Level 42, the name of a band (named after the Hitchhikers usage).
• The year A.D. 42, 42 BC, and 1942.