Numbers / 809

The Number 809

809 is prime: only 1 and 809 divide it evenly; the next prime after 809 is 811. 809's proper divisors total just 1, 808 short of 809, the deficient case most of 809's neighbors share too. 809 has a digit sum of 17; for 809, the digital root works out to 8. 809 shares no factor with 2-12; 809's own divisors start beyond that range. 809 is 1100101001 in binary and 329 in hex; as a Roman numeral it's DCCCIX.