517 = 11 x 47.
517 is the smallest number n such that n + sigma(n) + sigma(sigma(n)) is a cube, where sigma(n) is the sum of all divisors of n.
517 is the sum of five consecutive prime numbers: 517 = 97 + 101 + 103 + 107 + 109.
517 is a Smith number. A Smith number is a composite number for which, in a given base, the sum of its digits is equal to the sum of the digits in its prime factorization: 5 + 1 + 7 = 1 + 1 + 4 + 7.
517 is the telephone area code that covers Lansing, Mich., and neighboring areas.
Source: Number Gossip