Q: What are the prime factors of the number 31,421,440?

 A: 2, 5, 17, 19

Why are those the prime factors of the number 31,421,440?

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 31,421,440

31,421,440
Factor Arrows
215,710,720
Factor Arrows
27,855,360
Factor Arrows
23,927,680
Factor Arrows
21,963,840
Factor Arrows
2981,920
Factor Arrows
2490,960
Factor Arrows
2245,480
Factor Arrows
2122,740
Factor Arrows
261,370
Factor Arrows
230,685
Factor Arrows
56,137
Factor Arrows
17361
Factor Arrows
1919

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, 17, 19

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 2 x 2 x 2 x 5 x 17 x 19 x 19 = 31,421,440

This can also be written as 210 x 51 x 171 x 192 = 31,421,440

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


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