Yes, 2,003 is a prime number. Its only factors are 1 and 2,003.
A number is prime if no smaller prime up to its square root divides it. The square root of 2,003 is about 44.75, so it is enough to test the primes 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41 and 43.
| Divide by | Remainder | Divides evenly? |
|---|---|---|
| 2 | 1 | No |
| 3 | 2 | No |
| 5 | 3 | No |
| 7 | 1 | No |
| 11 | 1 | No |
| 13 | 1 | No |
| 17 | 14 | No |
| 19 | 8 | No |
| 23 | 2 | No |
| 29 | 2 | No |
| 31 | 19 | No |
| 37 | 5 | No |
| 41 | 35 | No |
| 43 | 25 | No |
None of them divides 2,003 evenly, so 2,003 is prime.
| Number | Prime? |
|---|---|
| 1,801 | Yes |
| 1,901 | Yes |
| 1,999 | Yes |
| 2,001 | No, 3 × 23 × 29 |
| 2,017 | Yes |
| 2,020 | No, 2 × 2 × 5 × 101 |
| 2,021 | No, 43 × 47 |
| 2,023 | No, 7 × 17 × 17 |
More about 2003: 2003 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.