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Q:

# What are the factors of 21?

A:

The factors of 21 are 1, 3, 7 and 21. A factor is a number that can divide evenly into a given number. Because 21 can be divided by numbers other than itself and 1, it is called a composite number.

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Every number has 1 and itself as a factor. Numbers that have no other factors are called prime numbers. To determine if 21 has other factors, a person would look to see if it is an even number. Because 21 is not, it cannot be divided by 2. Therefore, the individual would start by dividing by 3. The result is 7, which makes 3 and 7 both factors of 21. Next, 4, 5, and 6 would be tried. None of those can divide evenly into 21, so they are not factors.

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## Related Questions

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The two factors of 17 are 1 and 17. Because 17 only has one set of factors, or factor pair, it is a prime number. This means it can only be divided by 1 and itself.

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The factors of 27 are one, three, nine and 27. The factors of a particular number are those numbers that divide evenly into it. One and the number itself are always factors of any given number.

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The factors of the number 38 are 1, 2, 19 and 38. For any positive number, the number 1 and the number itself are factors, so 1 and 38 are inherent factors. Additional numbers that divide 38 evenly are 2 and 19.