Q: What are the prime factors of the number 685,720?

 A: 2, 5, 7, 31, 79

Why are those the prime factors of the number 685,720?

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 685,720

685,720
Factor Arrows
2342,860
Factor Arrows
2171,430
Factor Arrows
285,715
Factor Arrows
517,143
Factor Arrows
72,449
Factor Arrows
3179

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, 31, 79

We can check our work by multiplying all of the prime factors together: 2 x 2 x 2 x 5 x 7 x 31 x 79 = 685,720

This can also be written as 23 x 51 x 71 x 311 x 791 = 685,720

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


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