Q: What are the prime factors of the number 400,321,440?

 A: 2, 3, 5, 17, 23, 79

Why are those the prime factors of the number 400,321,440?

Prime factors are the prime numbers that can be multipled together to equal the original number. You find the factors by dividing by prime numbers. It is best shown by creating a Factor Tree.

Factor Tree for the number 400,321,440

400,321,440
Factor Arrows
2200,160,720
Factor Arrows
2100,080,360
Factor Arrows
250,040,180
Factor Arrows
225,020,090
Factor Arrows
212,510,045
Factor Arrows
34,170,015
Factor Arrows
31,390,005
Factor Arrows
3463,335
Factor Arrows
3154,445
Factor Arrows
530,889
Factor Arrows
171,817
Factor Arrows
2379

The numbers in bold above are the prime factors. If there are multiples, you only count them one time. This leads us to our prime factors of:

2, 3, 5, 17, 23, 79

We can check our work by multiplying all of the prime factors together: 2 x 2 x 2 x 2 x 2 x 3 x 3 x 3 x 3 x 5 x 17 x 23 x 79 = 400,321,440

This can also be written as 25 x 34 x 51 x 171 x 231 x 791 = 400,321,440

If you would like to know more, or need additional explanation, please review our prime factorization explanation.


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