Q: What are the prime factors of the number 21,152,320?

 A: 2, 5, 7, 19, 71

Why are those the prime factors of the number 21,152,320?

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 21,152,320

21,152,320
Factor Arrows
210,576,160
Factor Arrows
25,288,080
Factor Arrows
22,644,040
Factor Arrows
21,322,020
Factor Arrows
2661,010
Factor Arrows
2330,505
Factor Arrows
566,101
Factor Arrows
79,443
Factor Arrows
71,349
Factor Arrows
1971

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, 19, 71

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 5 x 7 x 7 x 19 x 71 = 21,152,320

This can also be written as 26 x 51 x 72 x 191 x 711 = 21,152,320

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


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