The sum of the digits of a number is subtracted from the number. The resulting number is always divisible by which number?

The resulting number is always divisible by 9.

Let's take a number with digits a, b, and c. The number can be represented as 100a + 10b + c.

The sum of the digits is a + b + c.

When we subtract the sum of the digits from the number, we get:

100a + 10b + c - (a + b + c) = 99a + 9b

This resulting number is always divisible by 9, as 99a + 9b = 9(11a + b), which is a multiple of 9.

9