42

42 = 2 x 3 x 7.

42 is a Catalan number.

42 lies between a twin prime pair: 41, 43.

42 is the number of spots on a pair of dice.

42 is 101010 in base 2 (binary).

42 has a unique representation as a sum of three squares: 42 = 1² + 4² + 5².


Douglas Adams used 42 as "the answer to the ultimate question of life, the universe, and everything" in his Hitchhiker's Guide to the Galaxy series.

Source: Number Gossip