Q: What are the prime factors of the number 30,720?

 A: 2, 3, 5

Why are those the prime factors of the number 30,720?

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 30,720

30,720
Factor Arrows
215,360
Factor Arrows
27,680
Factor Arrows
23,840
Factor Arrows
21,920
Factor Arrows
2960
Factor Arrows
2480
Factor Arrows
2240
Factor Arrows
2120
Factor Arrows
260
Factor Arrows
230
Factor Arrows
215
Factor Arrows
35

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, 5

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 3 x 5 = 30,720

This can also be written as 211 x 31 x 51 = 30,720

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


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