Calculators

Math

Factors

18 is twice the perfect square 9 and is commonly used in age-related contexts (voting, adulthood). It has 6 factors.

All Factors

The factors of 18 are:  1, 2, 3, 6, 9, 18

The prime factorization is: 18 = 2 x 3 x 3

Factoring of 18 Using Trial Division

Find the Factors of 18 :

• Calculate the square root of 18 which is 4.2426, and round it down to the closest whole number, 4, and use it in the next step.
• Test the integer values 1 through 4 for division into 18 where the remainder equals 0.
• We find 6 factors where the remainder of division is 0 and they are: 1, 2, 3, 6, 9, 18.

Factor Pairs

1 × 18 = 18
2 × 9 = 18
3 × 6 = 18

The factor pairs (multiples) that equal 18 when multiplied together are: (1 and 18), (2 and 9), (3 and 6), which we found by matching up all factors of 18 which are: 1, 2, 3, 6, 9, 18.

Is 18 Prime or Composite?

18 is a composite number. Since it has more than two factors, we know that 18 is not prime, it is composite. Prime numbers only have two factors. They are evenly divisible by only 1 and itself.