1- Every whole number are divisible by 1.
2-All even numbers (ending in 0,2,4,6,8).
3-If the sum of the number is divisible by 3.
4-If the number is divisible by 2 twice.
5-If it ends in 0,5.
6-If it is divisible by 2 and 3.
7-You can double the last digit and subtract the sum from the rest of the number, and set an answer that is divisible by 7 ( including 0).