Factors of 561

How to find the factors of 561

Test every whole number from 1 up to the square root of 561 (√561 ≈ 23.685). Each number that divides evenly gives you two factors at once: the divisor and the quotient.

• 561 ÷ 1 = 561 — so 1 and 561 are factors
• 561 ÷ 2 = 280.5 — not a whole number
• 561 ÷ 3 = 187 — so 3 and 187 are factors
• 561 ÷ 4 = 140.25 — not a whole number
• 561 ÷ 5 = 112.2 — not a whole number
• 561 ÷ 6 = 93.5 — not a whole number
• 561 ÷ 7 = 80.143 — not a whole number
• 561 ÷ 8 = 70.125 — not a whole number
• 561 ÷ 9 = 62.333 — not a whole number
• 561 ÷ 10 = 56.1 — not a whole number
• 561 ÷ 11 = 51 — so 11 and 51 are factors
• 561 ÷ 12 = 46.75 — not a whole number
• 561 ÷ 13 = 43.154 — not a whole number
• 561 ÷ 14 = 40.071 — not a whole number
• 561 ÷ 15 = 37.4 — not a whole number
• 561 ÷ 16 = 35.063 — not a whole number
• 561 ÷ 17 = 33 — so 17 and 33 are factors
• 561 ÷ 18 = 31.167 — not a whole number
• 561 ÷ 19 = 29.526 — not a whole number
• 561 ÷ 20 = 28.05 — not a whole number
• 561 ÷ 21 = 26.714 — not a whole number
• 561 ÷ 22 = 25.5 — not a whole number
• 561 ÷ 23 = 24.391 — not a whole number

Collecting both numbers from every successful division gives the complete list: 1, 3, 11, 17, 33, 51, 187 and 561.

Prime factorization of 561

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

The primes you divided by give 561 = 3 × 11 × 17. From the exponents you can also count the factors without listing them: (1 + 1) × (1 + 1) × (1 + 1) = 8.

Properties of 561

• 561 is a composite number.
• The sum of all its factors is 864; the sum of its proper factors (excluding 561) is 303, which makes it a deficient number (its proper factors add up to less than itself).
• 561 is not a perfect square, so its factors pair up evenly.
• Multiples of 561 include 1,122, 1,683, 2,244, 2,805 and so on.

Factors vs. multiples

Factors of 561 are the numbers that divide into it; multiples of 561 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.