#### Numbers that are only dividing by themselves and by number 1 are called prime numbers.

#### A composite number is a positive integer that has at least one positive divisor other than 1 and the number itself. A composite number is also any positive integer greater than 1 that is not a prime number.

- 2 is divisible only by 2 and 1, so 2 is a prime number
- 3 is divisible only by 3 and 1, so 3 is a prime number
- 5 is divisible only by 5 and 1, so 5 is a prime number
- 13 is divisible only by 13 and 1, so 13 is a prime number

### 1 is not considered prime, so **the first prime number is 2** (prime numbers list is starting with the number 2)

**Examples of prime numbers, up to 100:** 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

### EUCLID (300 B.C.) proved that the set of prime numbers is infinite, with **no largest prime number**.