Q: What are the prime factors of the number 21,221,376?

 A: 2, 3, 11, 157

Why are those the prime factors of the number 21,221,376?

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 21,221,376

21,221,376
Factor Arrows
210,610,688
Factor Arrows
25,305,344
Factor Arrows
22,652,672
Factor Arrows
21,326,336
Factor Arrows
2663,168
Factor Arrows
2331,584
Factor Arrows
2165,792
Factor Arrows
282,896
Factor Arrows
241,448
Factor Arrows
220,724
Factor Arrows
210,362
Factor Arrows
25,181
Factor Arrows
31,727
Factor Arrows
11157

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, 3, 11, 157

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 2 x 2 x 3 x 11 x 157 = 21,221,376

This can also be written as 212 x 31 x 111 x 1571 = 21,221,376

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


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