Divisible. A number is divisible by another number if it can be divided equally by that number; that is, if it yields a whole number when divided by that number. 12 is divisible by 4 because 12/4 = 3, and 3 is a whole number. 12 is not divisible by 10, because 12/10 = 1.2, and 1.2 is not a whole number.