Yes, 73 is a prime number. Its only factors are 1 and 73.
A number is prime if no smaller prime up to its square root divides it. The square root of 73 is about 8.54, so it is enough to test the primes 2, 3, 5 and 7.
| Divide by | Remainder | Divides evenly? |
|---|---|---|
| 2 | 1 | No |
| 3 | 1 | No |
| 5 | 3 | No |
| 7 | 3 | No |
None of them divides 73 evenly, so 73 is prime.
| Number | Prime? |
|---|---|
| 69 | No, 3 × 23 |
| 70 | No, 2 × 5 × 7 |
| 71 | Yes |
| 72 | No, 2 × 2 × 2 × 3 × 3 |
| 74 | No, 2 × 37 |
| 75 | No, 3 × 5 × 5 |
| 76 | No, 2 × 2 × 19 |
| 77 | No, 7 × 11 |
More about 73: factors of 73 · 73 squared · square root of 73 · 73 in binary · 73 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.