Q: What are the factor combinations of the number 640,480?

 A:
Positive:   1 x 6404802 x 3202404 x 1601205 x 1280968 x 8006010 x 6404816 x 4003020 x 3202432 x 2001540 x 1601280 x 8006160 x 4003
Negative: -1 x -640480-2 x -320240-4 x -160120-5 x -128096-8 x -80060-10 x -64048-16 x -40030-20 x -32024-32 x -20015-40 x -16012-80 x -8006-160 x -4003


How do I find the factor combinations of the number 640,480?

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 640,480, 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.

1 640,480
-1 -640,480

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 640,480.

Example:
1 x 640,480 = 640,480
and
-1 x -640,480 = 640,480
Notice both answers equal 640,480

With that explanation out of the way, let's continue. Next, we take the number 640,480 and divide it by 2:

640,480 ÷ 2 = 320,240

If the quotient is a whole number, then 2 and 320,240 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 2 320,240 640,480
-1 -2 -320,240 -640,480

Now, we try dividing 640,480 by 3:

640,480 ÷ 3 = 213,493.3333

If the quotient is a whole number, then 3 and 213,493.3333 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 2 320,240 640,480
-1 -2 -320,240 -640,480

Let's try dividing by 4:

640,480 ÷ 4 = 160,120

If the quotient is a whole number, then 4 and 160,120 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 4 160,120 320,240 640,480
-1 -2 -4 -160,120 -320,240 640,480
Keep dividing by the next highest number until you cannot divide anymore.

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

124581016203240801604,0038,00616,01220,01532,02440,03064,04880,060128,096160,120320,240640,480
-1-2-4-5-8-10-16-20-32-40-80-160-4,003-8,006-16,012-20,015-32,024-40,030-64,048-80,060-128,096-160,120-320,240-640,480

More Examples

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