WorkedMathGlossary

Factors of 20

The factors of 20 are 1, 2, 4, 5, 10, 20. No, 20 is a composite number. Its prime factorization is 2^2 × 5.

Factors of 20
1, 2, 4, 5, 10, 20
6 factors
Prime or Composite
Composite
Perfect Square
No
Prime Factorization
2^2 × 5
Sum of Factors
42 (22 without 20 itself)

Factor pairs of 20

Every factor has a partner that multiplies with it to give 20. Listing pairs from the outside in is the fastest way to find all the factors: once the two numbers in a pair meet in the middle, you have them all.

PairCheck
1 and 201 × 20 = 20
2 and 102 × 10 = 20
4 and 54 × 5 = 20

Prime factorization of 20, step by step

Divide by the smallest prime that goes in evenly, then repeat on the result until you reach 1. The divisors you used are the prime factors.

StepDivideResult
120 ÷ 210
210 ÷ 25
35 ÷ 51

So 20 = 2 × 2 × 5, written compactly as 2^2 × 5.

Divisibility checks for 20

The quick rules a student uses before dividing, applied to 20:

Divisible byRuleFor 20Result
2last digit is evenlast digit 0yes
3digit sum divisible by 3digits add to 2no
4last two digits divisible by 420 ÷ 4yes
5last digit is 0 or 5last digit 0yes
6divisible by both 2 and 3even, digit sum 2no
8last three digits divisible by 820 ÷ 8no
9digit sum divisible by 9digits add to 2no
10last digit is 0last digit 0yes

Frequently Asked Questions

What are the factors of 20?

The factors of 20 are 1, 2, 4, 5, 10, 20.

Is 20 a prime number?

No, 20 is a composite number. Its prime factorization is 2^2 × 5.

How many factors does 20 have?

20 has 6 factors. You can get that count from the prime factorization without listing them: add 1 to each exponent in 2^2 × 5 and multiply -- (2+1) × (1+1) = 6.

Is 20 even or odd?

20 is even (2 is one of its factors).

What is the sum of the factors of 20?

1 + 2 + 4 + 5 + 10 + 20 = 42. Leaving out 20 itself, the proper factors add to 22, more than 20, so 20 is an abundant number.

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