Q: What are the prime factors of the number 21,705,250?

 A: 2, 5, 7, 79, 157

Why are those the prime factors of the number 21,705,250?

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 21,705,250

21,705,250
Factor Arrows
210,852,625
Factor Arrows
52,170,525
Factor Arrows
5434,105
Factor Arrows
586,821
Factor Arrows
712,403
Factor Arrows
79157

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, 79, 157

We can check our work by multiplying all of the prime factors together: 2 x 5 x 5 x 5 x 7 x 79 x 157 = 21,705,250

This can also be written as 21 x 53 x 71 x 791 x 1571 = 21,705,250

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


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