What are the prime factors of 40?

The prime factors of 40 are 2 x 2 x 2 x 5. Prime factors are prime numbers, which are only divisible by 1 and themselves. The only even prime number is 2, and it is a factor of all even numbers.

Because 40 is even, determining its prime factors begins with dividing by 2, leaving the factors of 2 and 20. Since 20 is even, it is not prime, so it is necessary to divide by 2 again, leaving factors of 2, 2 and 10. A final division by 2 shows the prime factors of three 2s and a 5. Every number has its own unique set of prime factors.