Q: What are the prime factors of the number 21,531,825?

 A: 3, 5, 7, 31

Why are those the prime factors of the number 21,531,825?

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 21,531,825

21,531,825
Factor Arrows
37,177,275
Factor Arrows
32,392,425
Factor Arrows
3797,475
Factor Arrows
3265,825
Factor Arrows
553,165
Factor Arrows
510,633
Factor Arrows
71,519
Factor Arrows
7217
Factor Arrows
731

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:

3, 5, 7, 31

We can check our work by multiplying all of the prime factors together: 3 x 3 x 3 x 3 x 5 x 5 x 7 x 7 x 7 x 31 = 21,531,825

This can also be written as 34 x 52 x 73 x 311 = 21,531,825

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


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