Forty-two is a natural integer that follows 41 and precedes 43. It is an even number and a composite with eight positive divisors; among its proper divisors are 1, 2, 3, 6, 7, 14 and 21. The list of divisors and basic facts about its arithmetic make 42 a compact example in elementary number discussions (divisors).
Mathematical properties
In prime factorization 42 = 2 × 3 × 7, the product of three distinct primes, which classifies it as a sphenic number (sphenic). It is also pronic because it equals the product of two consecutive integers (6 × 7). The sum of 42's proper divisors is 54, greater than 42, so it is an abundant number (abundant). Other notable arithmetic identities include that 42 is a Harshad number in base 10 (divisible by the sum of its digits) and that the fifth Catalan number equals 42, a point of interest in combinatorics.
History and cultural significance
Beyond mathematics, 42 appears frequently in culture and science. It is the atomic number of the element molybdenum, and in computing the ASCII code for the asterisk character '*' is 42, a fact often cited by programmers. The number gained particular fame through popular literature: Douglas Adams used 42 as a humorous "Answer to the Ultimate Question" in his science fiction series, which helped cement the number's place in modern popular culture.
Uses and occurrences
42 recurs in examples across disciplines. In programming and puzzles it is frequently chosen as a sample value or placeholder, and in mathematics it provides compact examples of several concepts (sphenic, pronic, abundant, Catalan). In sport and history the number is notable as the jersey number of Jackie Robinson, which has been widely commemorated. Enthusiasts of recreational mathematics and number theory often collect and document additional curiosities connected to 42.
Notable distinctions
The appeal of 42 lies in the density of interesting properties packed into a small integer: simple factorization, a role in combinatorics, appearances in science and computing, and a strong presence in popular culture. Those qualities make it a frequent example when illustrating the interplay between abstract arithmetic properties and real-world references.
For further reading on basic definitions and related sequences, introductory texts and online resources provide accessible treatments of terms such as pronic, sphenic and abundant numbers, and they place 42 within broader integer sequences and combinatorial identities.