Number 1

Dividing any number by the number 1 will result in the other number. For example 20 divided by 1 equals 20. Remember that using 1 as the divisor, the answer will always be the same as the original dividend.

Number 2

When dividing by 2, remember that you are always taking the other number in the equation and splitting it in half. For example, half of 20 is 10, so therefore 20 divided by 2 equals 10.

Number 3

To find out if a number is divisible by 3, add up all the digits in the dividend, and then see if that answer is divisible by 3. Using 261 as an example: 2 + 6 + 1 = 9. 9 is evenly divisible by 3, so the full number 261 is as well.

Number 4

No matter how large a number, you will know if it is evenly divisible by 4 if the last two digits are divisible by 4. For example, 755,891,453,012 is divisible by 4, because the number formed by the last two digits -- 12 -- is divisible by 4.

Number 5

You will know if a number may be evenly divided by 5 if the last digit in the dividend is a 5 or a 0. For example, both 40 and 23,562,395 end in either 5 or 0, so so they are both divisible by 5.

Number 6

Remembering the trick for number 3, add together the digits of a multi-digit dividend to see if it is divisible by 3. If the last digit of that dividend is also even, then the dividend is also divisible by 6. For example, 52,356, ends in 6 (an even number), and when the digits are all added together (5 + 2 + 3 + 5 + 6 = 21), the sum is divisible by 3. Therefore, the dividend is also divisible by 6. If the number is too large to tell, continue this process until you are left with a single digit number. In the same example, if you do not know whether 21 is divisible by 3, then add 2 and 1 to make 3. 3 is divisible by 3.

Number 7

To see if you can evenly divide a number by 7, double the last digit and subtract it from the rest of the number. If the number with which you are left is divisible by 7, so is the original number. For example, in 112, the last digit is a 2. Multiply it by 2 to get 4. Subtract 4 from the first two digits, 11, to get 7. 7 is divisible by 7, so you will know that 112 is also divisible by 7.

Number 8

A trick for the number 8 works best for numbers greater than 1,000, because the last three digits of the number reveal the trick. If the last three numbers are divisible by 8, then the entire number will be as well. For example, in the number 421,472, the number formed by the last three digits, 472, is divisible by 8, so therefore the entire number will also be divisible by 8. If the last three digits of the dividend are 000, the entire number will also be divisible by 8.

Number 9

Once again, remember the number 3 trick. If you add together the digits of the dividend and find that they are divisible by 9, the original number will be as well. For example, in 531, 5 + 3 + 1 = 9, so 531 is divisible by 9.

Number 10

As with the trick for number 5, the last digit of the number will guide you. If the last digit is a 0, then the entire number will be evenly divisible by 10.