Numbers / 421

The Number 421

421 is prime: only 1 and 421 divide it evenly; the next prime after 421 is 431. 421's proper divisors total just 1, 420 short of 421, the deficient case most of 421's neighbors share too. 421 has a digit sum of 7; for 421, the digital root works out to 7. 421 shares no factor with 2-12; 421's own divisors start beyond that range. 421 is 110100101 in binary and 1A5 in hex; as a Roman numeral it's CDXXI.