309

309 = 3 x 103.

309 is a centered hendecagonal number.

309 is the smallest number whose fifth power (309⁵ = 2817036000549) is pandigital (contains every digit from 0 to 9 at least once).

309³ + 309⁰ + 309⁹ is a prime, with prime digital length.

309 is 373 in base 9. It is 621 in base 7 and 261 in base 11.

309 is a telephone area code serving the state of Illinois.

Source: Number Gossip