Q: What are the prime factors of the number 645?

Why are those the prime factors of the number 645?

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 645

	645
3		215
	5		43

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:

3, 5, 43

We can check our work by multiplying all of the prime factors together: 3 x 5 x 43 = 645

This can also be written as 3¹ x 5¹ x 43¹ = 645

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

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