Numbers / 191

The Number 191

191 is prime: only 1 and 191 divide it evenly; the next prime after 191 is 193. 191's proper divisors total just 1, 190 short of 191, the deficient case most of 191's neighbors share too. 191 is also a palindrome, since 191 reads identically forwards and backwards. 191 has a digit sum of 11; for 191, the digital root works out to 2. 191 shares no factor with 2-12; 191's own divisors start beyond that range. 191 is 10111111 in binary and BF in hex; as a Roman numeral it's CXCI.