Factors of 15

All factors of 15

Here are all 4 factors of 15, listed from smallest to largest.

Factor pairs of 15

These 2 pairs of whole numbers each multiply to give 15.

Prime factorization of 15

Dividing 15 by the smallest prime at each step gives its prime factorization:

The distinct prime factors of 15 are 3, 5. To factorize any other number, use the prime factorization calculator.

Factor tree of 15

A factor tree shows the same prime factorization visually. Each composite branch splits until every endpoint is a prime number.

Properties of 15

What makes 15 interesting

• 15 is a composite number, meaning it has more than two factors. It can be written as a product of smaller whole numbers in 2 different ways.
• 15 is a deficient number: its proper factors sum to 9, which is 6 less than 15 itself.
• 15 is a triangular number — it is the sum of the first 5 whole numbers (1 + 2 + … + 5 = 15).

How to find the factors of 15 yourself

Divide 15 by each whole number starting from 1. Whenever the division leaves no remainder, both the divisor and the quotient are factors. You only need to test up to √15 ≈ 3.87, because every factor above that pairs with one below it.

Reading both columns gives every factor: 1, 3, 5, 15. The factor calculator does this automatically for any number.