2: If the number is even, it is divisible by 2.

3: If the sum of the digits of the number is divisible by 3, then the number is as well.

4: If the last two digits of the number make a number that is divisible by 4, then the number is as well.

5: If the last digit of the number is five or zero, the number is divisible by five.

6: If the rules for both 2 and 3 work, the number is divisible by six.

7: Mark out the last digit, double it, and subtract it from the remaining number. Repeat this process until it is easily determined if the remaining number is divisible by seven.

8: If the last three digits of the number make a number that is divisible by 8, then the number is as well.

9: If the sum of the digits of the number is divisible by 9, then the number is as well.

10: If the last digit is zero, then the number is divisible by ten.

11: Starting at one’s place, add every other digit. Next, add the remaining digits. Subtract the two sums. If the answer is divisible by eleven, so is the original number.

12: If the rules for both 3 and 4 work, the number is divisible by twelve.

13: Starting at one’s place, group the digits into groups of three. Next, add every other group of three digit numbers. Next, add the remaining three digit numbers. Subtract the two sums. If the answer is divisible by thirteen, so is the original number.