Numbers / 509

The Number 509

509 is prime: only 1 and 509 divide it evenly; the next prime after 509 is 521. 509's proper divisors total just 1, 508 short of 509, the deficient case most of 509's neighbors share too. 509 has a digit sum of 14; for 509, the digital root works out to 5. 509 shares no factor with 2-12; 509's own divisors start beyond that range. 509 is 111111101 in binary and 1FD in hex; as a Roman numeral it's DIX.