491 is a prime number. It is a Sophie Germain prime (A005384) because 2 x 491 + 1 = 983 is also prime.
491 is a prime number with distinct, nonprime digits (A034844) in English consecutive order: four, nine, one. Each digit is also a square.
It is conjectured that 491 is the smallest prime not of the form x3 + y3 + 2z3.
491 is the smallest number n such that the largest prime factors of the numbers n through n + 4 decrease.
Source: Prime Curios!