Q: What are the factor combinations of the number 108?

 A:
Positive:   1 x 1082 x 543 x 364 x 276 x 189 x 12
Negative: -1 x -108-2 x -54-3 x -36-4 x -27-6 x -18-9 x -12


How do I find the factor combinations of the number 108?

Unfortunately, there's not simple formula to identifying all of the factors of a number and it can be a tedious process when trying to identify the divisors of larger numbers. To find the factor combinations of the number 108, it is easier to work with a table - it's called factoring from the outside in.

Outside in Factoring

We start by creating a table and writing 1 on the left side and then the number we're trying to find the factors for on the right side in a table. Then, below that, write the numbers as a negative as well.

1 108
-1 -108

Why are the negative numbers included?

When you multiply two negative numbers together, you get a positive number. That means both the positive and negative numbers are factors of 108.

Example:
1 x 108 = 108
and
-1 x -108 = 108
Notice both answers equal 108

With that explanation out of the way, let's continue. Next, we take the number 108 and divide it by 2:

108 ÷ 2 = 54

If the quotient is a whole number, then 2 and 54 are factors. In this case, the quotient is a whole number. Write them in the table inside the other two factors like the below example. Don't forget to write the negative numbers too!

Here is what our table should look like at this step:

1 2 54 108
-1 -2 -54 -108

Now, we try dividing 108 by 3:

108 ÷ 3 = 36

If the quotient is a whole number, then 3 and 36 are factors. In this case, the quotient is a whole number. Write them in the table inside the other two factors like the below example. Don't forget to write the negative numbers too!

Here is what our table should look like at this step:

1 2 3 36 54 108
-1 -2 -3 -36 -54 -108

Let's try dividing by 4:

108 ÷ 4 = 27

If the quotient is a whole number, then 4 and 27 are factors. In this case, the quotient is a whole number. Write them in the table inside the other two factors like the below example. Don't forget to write the negative numbers too!

Here is what our table should look like at this step:

1 2 3 4 27 36 54 108
-1 -2 -3 -4 -27 -36 -54 108
Keep dividing by the next highest number until you cannot divide anymore.

If you did it right, you will end up with this table:

1234691218273654108
-1-2-3-4-6-9-12-18-27-36-54-108

More Examples

Here are some more numbers to try:

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