42

42 is an integer. In prime factorization, it equals 2 × 3 × 7, making it square-free. It is a pronic number, equal to 6 × 7. In base-10 representations, 42 is 42; in binary it is 101010; in octal 52; in hexadecimal 2A. The atomic number of molybdenum is 42.

Mathematically, 42 is the fifth Catalan number (C5 = 42) and a sphenic number, the product of three distinct primes. It is a Harshad number in base 10 since the sum of digits is 6 and 42 ÷ 6 = 7. It also equals the sum of the first six even numbers: 2 + 4 + 6 + 8 + 10 + 12 = 42.

In culture and science, 42 has several notable associations. In The Hitchhiker's Guide to the Galaxy, it is described as the answer to the ultimate question of life, the universe, and everything. Jackie Robinson’s number 42 was retired across Major League Baseball in his honor. Messier 42 (M42) is the Orion Nebula, a well-known astronomical object. In ASCII encoding, the decimal value 42 corresponds to the asterisk (*) character.