Quick answer: The factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18 and 36: nine factors in five pairs (1 × 36, 2 × 18, 3 × 12, 4 × 9, 6 × 6), adding up to 91.
How it's calculated
Divide the number by 1, 2, 3 and so on up to its square root. Each divisor d that leaves no remainder gives a pair: d and n ÷ d. Past the square root the pairs only repeat.
A number with exactly two factors, 1 and itself, is prime. A perfect square has an odd number of factors because one pair is a number times itself (6 × 6 = 36).
To break a number into primes, use prime factorization; for factors shared by several numbers, use the common factors calculator.
Worked examples
- 36: 1, 2, 3, 4, 6, 9, 12, 18, 36 (9 factors, sum 91)
- 28: 1, 2, 4, 7, 14, 28 (sum 56 = 2 × 28, a perfect number)
- 97: 1, 97 (prime)
Frequently asked questions
What is the difference between a factor and a multiple?
A factor divides the number (3 is a factor of 12); a multiple is the number times a whole number (12 is a multiple of 3).
Why stop at the square root?
If d × e = n and d is larger than √n, then e is smaller than √n and was already found, so every pair appears before the square root.
How large a number can I factor?
Up to one trillion (10¹²). The calculation runs in your browser.
What are the factors of 36?
1, 2, 3, 4, 6, 9, 12, 18 and 36. That's nine, an odd count, because 6 × 6 pairs with itself.
Is 1 a prime number?
No. A prime needs exactly two factors, 1 and itself, and 1 only has one.
What is a perfect number?
One that equals the sum of its other factors. 6 is 1 + 2 + 3, and 28 is 1 + 2 + 4 + 7 + 14.