At some point we all dedicated a significant amount of time to learning about divisors and long and short division. What was that 3rd, 4th grade? Whichever year it was, it’s been a while. While it’s easy to devalue some of those skills the more we use calculators, there are some great advantages to being  able to conduct basic and complex math problems on our own.  Not only do you boost your cognitive ability and increase neural connections, you also expand your capacity for critical reasoning.  So put away whatever technology you us as a crutch, and show off your smarts.

Here are some *divisibility tricks for the numbers 1 through 10 to help you do some quick calculations on your own.

1: any integer is divisible by 1.

2: any integer is divisible by 2 if its last digit is divisible by 2.

3: any integer is divisible by 3 if all of the digits in the number add up to a number that is divisible by 3. For example, 171 is divisible by 3 because 1+7+1 =9, and 9 is divisible by 3.

4: any integer is divisible by 4 if its last two digits are a number that is divisible by 4. For example 612 is divisible by 4 because 12 is divisible by 4.

5: any integer is divisible by 5 if it ends in a 5 or a 0.

6: any integer is divisible by 6 if it is divisible by 2 and 3 (see above tricks).

7: there is no trick.

8: any integer is divisible by 8 if its last 3 digits are divisible by 8. For example, 234,816 is divisible by 8 because 816 is divisible by 8.

9: any integer is divisible by 9 if the sum of its digits is divisible by 9. For example 23,061,141 is divisible by 9 because 2+3+0+6+1+1+4+1=18 which is divisible by 9.

10: any integer is divisible by 10 if it ends in a 0.

*any whole number, or integer, is divisible by a number if there is no remainder when that number is divided into it.