Harshad number

Summary

In recreational mathematics, a Harshad number (or Niven number) in a given number base is an integer that is divisible by the sum of its digits when written in that base. Harshad numbers in base $n$ are also known as $n$-harshad (or $n$-Niven) numbers. Because being a harshad number is determined according to the base the number is expressed in, a number can be a Harshad number many times over. So-called Trans-harshad numerals are sequences of the digits 0-9 which, in every base which uses all their digits, represent a Harshad number in that base.