547

547 is a prime number.

547 is a centered hexagonal number (or hex number) and a centered heptagonal number.

The number of primes between 6! and 7! is itself prime. 547 is the smallest odd prime to enumerate the primes between n! and (n + 1)! for any n.

547 is the smallest number that cannot be written using 11 copies of 11 and the operations +, -, x, /.

547 is 202021 in base 3 and 20203 in base 4. It is 4142 in base 4.

Source: Prime Curios!