42
42 is a composite number, famous as the fictional 'Answer to the Ultimate Question of Life, the Universe, and Everything' from The Hitchhiker's Guide to the Galaxy.
- Even
- Composite
Where 42 fits
Why 42 is special
42's cultural fame from Douglas Adams' novel gives it a media significance entirely disconnected from its fairly ordinary mathematical profile.
See 42 visually
Prime factorisation
42 = 2 × 3 × 7
These three primes are the building blocks of 42 — multiplying them together gives 42, and there's no other way to build 42 from primes.
Same number, different meanings
How 42 is understood across different contexts — never implying one meaning because of another.
- Mathematics
42's cultural fame from Douglas Adams' novel gives it a media significance entirely disconnected from its fairly ordinary mathematical profile.
- Culture
Douglas Adams said he chose forty-two because it was an ordinary, unremarkable number, and denied any hidden significance. The subsequent search for meaning in it is itself the joke's most durable effect.
- Technology & computing
Forty-two appears widely as a default, test value and in-joke across software, including in documentation examples and error messages. Its use is a deliberate reference rather than an arbitrary choice.
- History
The Hitchhiker's Guide to the Galaxy began as a BBC Radio 4 series in 1978, a year before Adams adapted it into the 1979 novel. Adams was later asked repeatedly why he chose 42 specifically, and consistently rejected fan theories seeking a hidden mathematical, scientific or numerological explanation — he said in later interviews and writing that he wanted an ordinary, unremarkable-looking number precisely so the joke was that the universe's ultimate answer is mundane, and that he simply picked it, sitting at his desk, as a number that seemed funny. The number's fame is therefore a documented fictional and cultural phenomenon, not a mathematical coincidence Adams intended to point to.
- Religion & belief
In ancient Egyptian funerary texts, forty-two assessors are addressed in the judgement of the dead, each denied a particular wrongdoing in turn. The number is generally connected to the forty-two administrative districts of Egypt, so the court of the afterlife mirrors the government of the living. This is a scholarly account rather than the tradition's own framing.
- Media & popular culture
42 is the fictional 'Answer to the Ultimate Question of Life, the Universe, and Everything' computed by the supercomputer Deep Thought in Douglas Adams' The Hitchhiker's Guide to the Galaxy (1979), and has since become a recurring cultural in-joke referencing the novel.
42 is part of
Factors & digit properties
- Divisors (8)
- 1, 2, 3, 6, 7, 14, 21, 42
- Prime factorisation
- 2 × 3 × 7
- Digit sum
- 6
- Digital root
- 6
Representations
- Decimal
- 42
- Scientific notation
- 4.200 × 10^1
Roman numerals
X L I I
XLII uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 0 1 0 1 0
1 × 32 + 0 × 16 + 1 × 8 + 0 × 4 + 1 × 2 + 0 × 1 = 42
Octal
5 2
5 × 8 + 2 × 1 = 42
Hexadecimal
2 a
2 × 16 + a × 1 = 42
Read as powers of two: 32 + 8 + 2 = 42.
In historical numeral systems
Egyptian
4 hobbles, 2 strokes
4 × 10 + 2 × 1 = 42. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
4 corner wedges + 2 vertical wedges
42 fits in a single sexagesimal place: 4 corner wedges + 2 vertical wedges.
Greek (Ionic)
mu, then beta, marked as a numeral
mu-beta + keraia
mu + beta written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
mem, then bet
mem-bet
mem (40) + bet (2) = 42, written in descending order.
Chinese numerals
sì shí èr
sì shí èr
四 before 十 multiplies it: 4 tens. 二 after it adds 2. The written form mirrors the arithmetic — "sì shí èr". The financial (anti-fraud) form is 肆拾貳.
Maya
2 dots (upper, twenties place) over 2 dots (lower, units place)
2 × 20 + 2 = 42. Places stack vertically with the smallest at the bottom, so the upper group is worth twenty times the lower.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Abundant number
- Harshad (Niven) number
Related numbers & connections
42 is a factor of 84 (42 × 2 = 84).
View 84 →42 appears in Numbers in culture and belief, the topic covering numbers that carry a documented cultural fact.
42 is the fictional 'Answer to the Ultimate Question' in The Hitchhiker's Guide to the Galaxy.
Mathematically related
Numbers Around Us
- appears inCulture and belief
why?
Strength 0.50, confidence "high".
Media association
- has media association withThe Hitchhiker's Guide to the Galaxy
why?
Strength 0.50, confidence "high".
Culture
Douglas Adams said he chose forty-two because it was an ordinary, unremarkable number, and denied any hidden significance. The subsequent search for meaning in it is itself the joke's most durable effect.
DocumentedCultureGeography: Originating in the United KingdomPeriod: 1979–
Technology & computing
Forty-two appears widely as a default, test value and in-joke across software, including in documentation examples and error messages. Its use is a deliberate reference rather than an arbitrary choice.
DocumentedTechnology & computingGeography: GlobalPeriod: 1980s–
History
The Hitchhiker's Guide to the Galaxy began as a BBC Radio 4 series in 1978, a year before Adams adapted it into the 1979 novel. Adams was later asked repeatedly why he chose 42 specifically, and consistently rejected fan theories seeking a hidden mathematical, scientific or numerological explanation — he said in later interviews and writing that he wanted an ordinary, unremarkable-looking number precisely so the joke was that the universe's ultimate answer is mundane, and that he simply picked it, sitting at his desk, as a number that seemed funny. The number's fame is therefore a documented fictional and cultural phenomenon, not a mathematical coincidence Adams intended to point to.
DocumentedHistory
Religion & belief
In ancient Egyptian funerary texts, forty-two assessors are addressed in the judgement of the dead, each denied a particular wrongdoing in turn. The number is generally connected to the forty-two administrative districts of Egypt, so the court of the afterlife mirrors the government of the living. This is a scholarly account rather than the tradition's own framing.
DocumentedReligion & beliefCulture: ancient Egyptian funerary texts
Media & popular culture
42 is the fictional 'Answer to the Ultimate Question of Life, the Universe, and Everything' computed by the supercomputer Deep Thought in Douglas Adams' The Hitchhiker's Guide to the Galaxy (1979), and has since become a recurring cultural in-joke referencing the novel.
DocumentedMedia & popular culture
Mathematics
Mathematically, 42 is fairly ordinary: an even composite number (2 × 3 × 7), an abundant number (its proper divisors add up to more than itself), and a Harshad number (divisible by its own digit sum, 4 + 2 = 6). None of these properties are individually rare or remarkable — part of what Douglas Adams found funny about picking it as 'the answer to everything' was precisely that it has no special mathematical significance.
DocumentedMathematics
Common questions
Why is 42 famous?
It's the fictional 'Answer to the Ultimate Question of Life, the Universe, and Everything' from Douglas Adams' The Hitchhiker's Guide to the Galaxy — a joke about how an unsatisfying, ordinary-looking number could be presented as a profound cosmic answer.
Why is 42 used in computing and internet jokes?
Mainly because of the Hitchhiker's Guide reference itself — the book became widely read in early hacker and programmer culture, and 42 was adopted as a recurring in-joke (for example, as a placeholder or 'magic number' in code) referencing the novel rather than any property of the number itself.
Did Douglas Adams intend a hidden meaning behind 42?
He said the opposite — in later interviews and writing, Adams was consistent that he picked 42 as a deliberately mundane, ordinary number, and explicitly rejected fan theories looking for a hidden mathematical or numerological explanation.
Is 42 a prime number?
No, 42 is not prime.
What are the factors of 42?
The factors of 42 are 1, 2, 3, 6, 7, 14, 21, 42.
What is 42 in Roman numerals?
42 in Roman numerals is XLII. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be XXXXII, which Roman inscriptions used freely — the strict subtractive form is a later convention.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 6 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026