# Factors of 15

The factors of a integer are the integers that go into the larger number an even number of times. For example, 5 is a factor of 15 because 5 goes in to 15 evenly 3 times.

But you're here for the factors of 15. The factors of 15 are 1, 3, 5, 15. You can divide 15 by each of these numbers and get an integer value, and that value is also a factor of 15. Depending on who you talk to 1 and 15 should not be included in the factor list since all numbers are divisible by 1 and itself. But we're including them here.

\LARGE \begin{aligned} 15 \div 1 &= 15 \\ 15 \div 3 &= 5 \\ 15 \div 5 &= 3 \\ 15 \div 15 &= 1 \\ \end{aligned}

And notice that as we go down the list and divide 15 by each of its factors, the answer is another factor.

## How many factors of 15

Looking at our lists above we can see that 15 has 4 positive factors.

## Negative Factors of 15

We've already seen that the factors for 15 are $$\Large 1, 3, 5, 15$$. But if you remember back to math class you'll know that if you multiply two negative numbers together you'll get a positive, and the same works with factors. So this set of factors can also be displayed as negative factors, in this case $$\Large -1, -3, -5, -15$$.

## Is 15 prime?

A prime number is one that only has two factors, 1 and itself.

No, 15 is not a prime number because it has more factors other than 1 and itself.