Q: What are the prime factors of the number 398,720?

 A: 2, 5, 7, 89

Why are those the prime factors of the number 398,720?

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 398,720

398,720
Factor Arrows
2199,360
Factor Arrows
299,680
Factor Arrows
249,840
Factor Arrows
224,920
Factor Arrows
212,460
Factor Arrows
26,230
Factor Arrows
23,115
Factor Arrows
5623
Factor Arrows
789

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, 5, 7, 89

We can check our work by multiplying all of the prime factors together: 2 x 2 x 2 x 2 x 2 x 2 x 2 x 5 x 7 x 89 = 398,720

This can also be written as 27 x 51 x 71 x 891 = 398,720

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


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