503

503 is a prime number.

503 is the smallest prime that is the sum of the cubes of the first n primes: 2³ + 3³ + 5³ +7³ = 503.

5! + 0! + 3! is a three-digit Mersenne prime.

503 is a number that cannot be written as a sum of three squares.


503 is Clark Kent's Metropolis apartment number in the "Superman" series.

Source: Prime Curios!