Factors of 399

How to find the factors of 399

Test every whole number from 1 up to the square root of 399 (√399 ≈ 19.975). Each number that divides evenly gives you two factors at once: the divisor and the quotient.

• 399 ÷ 1 = 399 — so 1 and 399 are factors
• 399 ÷ 2 = 199.5 — not a whole number
• 399 ÷ 3 = 133 — so 3 and 133 are factors
• 399 ÷ 4 = 99.75 — not a whole number
• 399 ÷ 5 = 79.8 — not a whole number
• 399 ÷ 6 = 66.5 — not a whole number
• 399 ÷ 7 = 57 — so 7 and 57 are factors
• 399 ÷ 8 = 49.875 — not a whole number
• 399 ÷ 9 = 44.333 — not a whole number
• 399 ÷ 10 = 39.9 — not a whole number
• 399 ÷ 11 = 36.273 — not a whole number
• 399 ÷ 12 = 33.25 — not a whole number
• 399 ÷ 13 = 30.692 — not a whole number
• 399 ÷ 14 = 28.5 — not a whole number
• 399 ÷ 15 = 26.6 — not a whole number
• 399 ÷ 16 = 24.938 — not a whole number
• 399 ÷ 17 = 23.471 — not a whole number
• 399 ÷ 18 = 22.167 — not a whole number
• 399 ÷ 19 = 21 — so 19 and 21 are factors

Collecting both numbers from every successful division gives the complete list: 1, 3, 7, 19, 21, 57, 133 and 399.

Prime factorization of 399

Divide by the smallest prime that fits, and keep going until the quotient is 1:

The primes you divided by give 399 = 3 × 7 × 19. From the exponents you can also count the factors without listing them: (1 + 1) × (1 + 1) × (1 + 1) = 8.

Properties of 399

• 399 is a composite number.
• The sum of all its factors is 640; the sum of its proper factors (excluding 399) is 241, which makes it a deficient number (its proper factors add up to less than itself).
• 399 is not a perfect square, so its factors pair up evenly.
• Multiples of 399 include 798, 1,197, 1,596, 1,995 and so on.

Factors vs. multiples

Factors of 399 are the numbers that divide into it; multiples of 399 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.