Numbers / 551

The Number 551

551 is composite: factorization 19 × 29. That gives 551 exactly 4 divisors: 1, 19, 29, 551. 551's proper divisors total just 49, 502 short of 551, the deficient case most of 551's neighbors share too. 551 has a digit sum of 11; for 551, the digital root works out to 2. 551 shares no factor with 2-12; 551's own divisors start beyond that range. 551 is 1000100111 in binary and 227 in hex; as a Roman numeral it's DLI.