2 - All the numbers that end in 2, 4, 6, 8, or 0. 5 - All the numbers that end in 5 or 0. (This is because ten is divisible by 2 and 5.) 3, 9 - The sum of the digits will always add up to a multiple of 3 or 9. This is because 9 is the last digit of decimal, and 9's only prime factor is 3.
