Numbers / 139

The Number 139

139 is prime: only 1 and 139 divide it evenly; the next prime after 139 is 149. 139's proper divisors total just 1, 138 short of 139, the deficient case most of 139's neighbors share too. 139 has a digit sum of 13; for 139, the digital root works out to 4. 139 shares no factor with 2-12; 139's own divisors start beyond that range. 139 is 10001011 in binary and 8B in hex; as a Roman numeral it's CXXXIX.