Question

A ________ is a whole number that divides another whole number with a remainder of 0

Answer 1

It's a factor. This concept is widely used throughout algebra, and you'll probably bump into it through the end of high school and beyond.

A common use is expressing a term in prime factorization, or reducing a number to its most base parts- primes. For example:

$20 = 4 * 5 = 2 * 2 * 5$

Of course, a number like 13 which is already prime is made up of itself and 1. Factors do not have to be primes. 20 is also reducible through combinations of 1, 2, 4, 5, 10, and 20. Prime factorization is just a handy example.

Basically, factors multiply with each other to create other numbers, and numbers can be reduced down to their factors.