No, 1 is not a prime number. A prime needs exactly two different factors, and 1 has only one. It is also not composite.
The smallest prime number is 2. By definition a prime has exactly two factors, 1 and itself, and the number 1 has just one factor.
| Number | Prime? |
|---|---|
| 2 | Yes |
| 3 | Yes |
| 4 | No, 2 × 2 |
| 5 | Yes |
More about 1: factors of 1 · 1 squared · square root of 1 · 1 in binary · 1 in Roman numerals.
Another number? Use the prime number checker for any value, or see the list of prime numbers.