Q: What are the prime factors of the number 71,680?

 A: 2, 5, 7

Why are those the prime factors of the number 71,680?

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 71,680

71,680
Factor Arrows
235,840
Factor Arrows
217,920
Factor Arrows
28,960
Factor Arrows
24,480
Factor Arrows
22,240
Factor Arrows
21,120
Factor Arrows
2560
Factor Arrows
2280
Factor Arrows
2140
Factor Arrows
270
Factor Arrows
235
Factor Arrows
57

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

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 5 x 7 = 71,680

This can also be written as 211 x 51 x 71 = 71,680

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


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