No, 243 is not a prime number. It is a composite number: its digits add up to 9, which is divisible by 3, so 243 is divisible by 3.
243 has divisors other than 1 and itself. The smallest is 3: 243 ÷ 3 = 81.
Prime factorization: 243 = 3 × 3 × 3 × 3 × 3 = 3⁵.
| Number | Prime? |
|---|---|
| 239 | Yes |
| 240 | No, 2 × 2 × 2 × 2 × 3 × 5 |
| 241 | Yes |
| 242 | No, 2 × 11 × 11 |
| 244 | No, 2 × 2 × 61 |
| 245 | No, 5 × 7 × 7 |
| 246 | No, 2 × 3 × 41 |
| 247 | No, 13 × 19 |
More about 243: 243 in binary.
Another number? Use the prime number checker for any value, or see the list of prime numbers.