A composite number is a positive integer that has at least one positive divisor other than 1 and the number itself.

Positive integers that are only dividing by themselves and 1 are called prime numbers.

A composite number is also any positive integer larger than 1 that is not a prime number.

Examples of composite numbers. Examples of numbers that are not composite, but prime.

According to the definition above, 1 is not a composite number; 1 is also not considered a prime number either, so the first composite number is 4 (composite numbers list starts by 4);

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;

4 is divisible by 4, 2 and 1, so 4 is not a prime number, it's a composite number; its prime factorization is 4 = 2^{2};

6 is divisible by 6, 3, 2 and 1, so 6 is not a prime number, it's a composite number; its prime factorization is 6 = 2 × 3;

8 is divisible by 8, 4, 2 and 1, so 8 is not a prime number, it's a composite number; its prime factorization is 8 = 2^{3};

9 is divisible by 9, 3, and 1, so 9 is not a prime number, it's a composite number; its prime factorization is 9 = 3^{2};

10 is divisible by 10, 5, 2 and 1, so 10 is NOT a prime number;

12 is divisible by 12, 6, 4, 3, 2 and 1, so 12 is NOT a prime number;