How to find the factors of 28
Test every whole number from 1 up to the square root of 28 (√28 ≈ 5.292). Each number that divides evenly gives you two factors at once: the divisor and the quotient.
- 28 ÷ 1 = 28 — so 1 and 28 are factors
- 28 ÷ 2 = 14 — so 2 and 14 are factors
- 28 ÷ 3 = 9.333 — not a whole number
- 28 ÷ 4 = 7 — so 4 and 7 are factors
- 28 ÷ 5 = 5.6 — not a whole number
Collecting both numbers from every successful division gives the complete list: 1, 2, 4, 7, 14 and 28.
Prime factorization of 28
Divide by the smallest prime that fits, and keep going until the quotient is 1:
The primes you divided by give 28 = 2² × 7. From the exponents you can also count the factors without listing them: (2 + 1) × (1 + 1) = 6.
Properties of 28
- 28 is a composite number.
- The sum of all its factors is 56; the sum of its proper factors (excluding 28) is 28, which makes it a perfect number — a rare case where the proper factors add up exactly to the number.
- 28 is not a perfect square, so its factors pair up evenly.
- Multiples of 28 include 56, 84, 112, 140 and so on.
Factors vs. multiples
Factors of 28 are the numbers that divide into it; multiples of 28 are the numbers it divides into. Every number has a limited set of factors but infinitely many multiples. To work with any other number, use the factors calculator, or find shared factors with the GCF calculator.
Frequently asked questions
What are the factors of 28?
The factors of 28 are 1, 2, 4, 7, 14 and 28. Each of these divides 28 with no remainder.
How many factors does 28 have?
28 has 6 positive factors, which form 3 factor pairs. Counting negative factors as well doubles that to 12.
What is the prime factorization of 28?
28 = 2² × 7. Its distinct prime factors are 2 and 7.
Is 28 a prime number?
No. 28 is composite because it has 6 factors, more than the two a prime number has.