Q: What are the factor combinations of the number 921?

 A:
Positive:   1 x 9213 x 307
Negative: -1 x -921-3 x -307


How do I find the factor combinations of the number 921?

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 921, 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.

1 921
-1 -921

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 921.

Example:
1 x 921 = 921
and
-1 x -921 = 921
Notice both answers equal 921

With that explanation out of the way, let's continue. Next, we take the number 921 and divide it by 2:

921 ÷ 2 = 460.5

If the quotient is a whole number, then 2 and 460.5 are factors. In this case, the quotient is not a whole number. Don't write anything down and try the next divisor.

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

1 921
-1 -921

Now, we try dividing 921 by 3:

921 ÷ 3 = 307

If the quotient is a whole number, then 3 and 307 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 3 307 921
-1 -3 -307 -921

Let's try dividing by 4:

921 ÷ 4 = 230.25

If the quotient is a whole number, then 4 and 230.25 are factors. In this case, the quotient is not a whole number. Don't write anything down and try the next divisor.

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

1 3 307 921
-1 -3 -307 921
Keep dividing by the next highest number until you cannot divide anymore.

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

13307921
-1-3-307-921

More Examples

Here are some more numbers to try:

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