The factors of 40 are the whole numbers that divide 40 exactly, leaving no remainder: 1, 2, 4, 5, 8, 10, 20, 40. Use the calculator above for any number, or read on for the factor pairs, prime factorization and properties of 40.
What are the factors of 40?
A factor of 40 is any whole number that divides 40 with no remainder. Listing them from smallest to largest, the factors of 40 are:
1, 2, 4, 5, 8, 10, 20, 40
So 40 is a composite number with 8 factors in total. Every number has 1 and itself as factors; the interesting work is finding the ones in between.
Factor pairs of 40
A factor pair is two numbers that multiply to give 40. The factor pairs of 40 are:
| Factor pair | Product |
|---|---|
| 1 × 40 | 40 |
| 2 × 20 | 40 |
| 4 × 10 | 40 |
| 5 × 8 | 40 |
Prime factorization of 40
The prime factorization breaks 40 down into a product of prime numbers only:
$$ 40 = 2^{3} \times 5 $$How to find the factors of 40, step by step
- Start at 1 — 1 divides every number, so 1 and 40 are always factors.
- Test each whole number from 2 upward: if it divides 40 exactly, it is a factor.
- Use factor pairs — each small factor gives a matching large factor, so you only need to test up to $\sqrt{40}$.
- List them in order to get all 8 factors of 40.
Factors versus multiples of 40
It is easy to mix these up. The factors of 40 are the numbers that divide into 40 (they are less than or equal to 40), while the multiples of 40 are what you get by multiplying 40 outward: 40, 80, 120, 160, and so on. In short: factors go in, multiples go out. 40 is an even number, and its smallest prime factor is 2.
Properties of 40
| Number of factors | 8 |
| Sum of factors | 90 |
| Sum of proper divisors | 50 |
| Prime or composite | Composite |
| Even or odd | Even |
| Perfect square | No |
| Prime factorization | 2^3 x 5 |
Is 40 abundant, deficient or perfect?
Number theorists classify a number by comparing it to the sum of its proper divisors (all its factors except itself). For 40, those proper divisors add up to 50, which makes 40 an abundant number (its proper divisors sum to 50, which is more than 40). Most numbers are deficient; abundant and perfect numbers are comparatively rare, which is what makes this property interesting.
Using the factors of 40 for GCF and LCM
The prime factorization $2^{3} \times 5$ is the shortcut for combining 40 with another number. To find the greatest common factor (GCF), take the primes 40 shares with the other number, each to the lowest power. For the least common multiple (LCM), take every prime that appears in either number, each to the highest power. This is why the prime factorization is worth writing down — it does the heavy lifting for fractions, ratios and simplification.
Related factors and tools
Explore more: Factors of 42 Factors of 36 Factors of 44. Or find the factors of any number with the Factor Calculator. Exponents are the reverse idea — see logarithms and read the formal reference on divisors at Wikipedia.