Question

A number n where if the sum of the dights of the number is divisible by n, then the number itself is divisible by n.

Answer 1

A number n where if the sum of the dights of the number is divisible by n, then the number itself is divisible by n.

If the sum of a number's digits is evenly divisible by 3, the number is divisible by 3.
If the sum of a number's digits is evenly divisible by 9, the number is evenly divisible by 9.