Factors of 991

How to find the factors of 991

Test every whole number from 1 up to the square root of 991 (√991 ≈ 31.480). Each number that divides evenly gives you two factors at once: the divisor and the quotient.

• 991 ÷ 1 = 991 — so 1 and 991 are factors
• 991 ÷ 2 = 495.5 — not a whole number
• 991 ÷ 3 = 330.333 — not a whole number
• 991 ÷ 4 = 247.75 — not a whole number
• 991 ÷ 5 = 198.2 — not a whole number
• 991 ÷ 6 = 165.167 — not a whole number
• 991 ÷ 7 = 141.571 — not a whole number
• 991 ÷ 8 = 123.875 — not a whole number
• 991 ÷ 9 = 110.111 — not a whole number
• 991 ÷ 10 = 99.1 — not a whole number
• 991 ÷ 11 = 90.091 — not a whole number
• 991 ÷ 12 = 82.583 — not a whole number
• 991 ÷ 13 = 76.231 — not a whole number
• 991 ÷ 14 = 70.786 — not a whole number
• 991 ÷ 15 = 66.067 — not a whole number
• 991 ÷ 16 = 61.938 — not a whole number
• 991 ÷ 17 = 58.294 — not a whole number
• 991 ÷ 18 = 55.056 — not a whole number
• 991 ÷ 19 = 52.158 — not a whole number
• 991 ÷ 20 = 49.55 — not a whole number
• 991 ÷ 21 = 47.19 — not a whole number
• 991 ÷ 22 = 45.045 — not a whole number
• 991 ÷ 23 = 43.087 — not a whole number
• 991 ÷ 24 = 41.292 — not a whole number
• 991 ÷ 25 = 39.64 — not a whole number
• 991 ÷ 26 = 38.115 — not a whole number
• 991 ÷ 27 = 36.704 — not a whole number
• 991 ÷ 28 = 35.393 — not a whole number
• 991 ÷ 29 = 34.172 — not a whole number
• 991 ÷ 30 = 33.033 — not a whole number
• 991 ÷ 31 = 31.968 — not a whole number

Collecting both numbers from every successful division gives the complete list: 1 and 991.

Prime factorization of 991

991 is a prime number, so it cannot be broken down any further. Its prime factorization is simply 991.

Properties of 991

• 991 is a prime number.
• The sum of all its factors is 992; the sum of its proper factors (excluding 991) is 1, which makes it a deficient number (its proper factors add up to less than itself).
• 991 is not a perfect square, so its factors pair up evenly.
• Multiples of 991 include 1,982, 2,973, 3,964, 4,955 and so on.

Factors vs. multiples

Factors of 991 are the numbers that divide into it; multiples of 991 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.