Yes, 173 is a prime number. Its only factors are 1 and 173.
A number is prime if no smaller prime up to its square root divides it. The square root of 173 is about 13.15, so it is enough to test the primes 2, 3, 5, 7, 11 and 13.
| Divide by | Remainder | Divides evenly? |
|---|---|---|
| 2 | 1 | No |
| 3 | 2 | No |
| 5 | 3 | No |
| 7 | 5 | No |
| 11 | 8 | No |
| 13 | 4 | No |
None of them divides 173 evenly, so 173 is prime.
| Number | Prime? |
|---|---|
| 169 | No, 13 × 13 |
| 170 | No, 2 × 5 × 17 |
| 171 | No, 3 × 3 × 19 |
| 172 | No, 2 × 2 × 43 |
| 174 | No, 2 × 3 × 29 |
| 175 | No, 5 × 5 × 7 |
| 176 | No, 2 × 2 × 2 × 2 × 11 |
| 177 | No, 3 × 59 |
More about 173: factors of 173 · square root of 173 · 173 in binary.
Another number? Use the prime number checker for any value, or see the list of prime numbers.