+ 10
A Smith number is a compositenumber for which, in a given base (in base 10 by default), the sum of its digits is equal to the sum of the digits in its prime factorization. For example, 378 = 2 à 3 à 3 à 3 à 7 is a Smith number since 3 + 7 + 8 = 2 + 3 + 3 + 3 + 7.
Source - https://en.m.wikipedia.org/wiki/Smith_number