No, 561 is not a prime number. It is a composite number: its digits add up to 12, which is divisible by 3, so 561 is divisible by 3.
561 has divisors other than 1 and itself. The smallest is 3: 561 ÷ 3 = 187.
Prime factorization: 561 = 3 × 11 × 17.
| Number | Prime? |
|---|---|
| 511 | No, 7 × 73 |
| 521 | Yes |
| 539 | No, 7 × 7 × 11 |
| 541 | Yes |
| 601 | Yes |
| 611 | No, 13 × 47 |
| 641 | Yes |
| 701 | Yes |
Another number? Use the prime number checker for any value, or see the list of prime numbers.