Numbers / 181

The Number 181

181 is prime: only 1 and 181 divide it evenly; the next prime after 181 is 191. 181's proper divisors total just 1, 180 short of 181, the deficient case most of 181's neighbors share too. 181 is also a palindrome, since 181 reads identically forwards and backwards. 181 has a digit sum of 10; for 181, the digital root works out to 1. 181 shares no factor with 2-12; 181's own divisors start beyond that range. 181 is 10110101 in binary and B5 in hex; as a Roman numeral it's CLXXXI.