Prime and composite numbers are both natural numbers. A natural number is any number that is one and above. They are written as follows: 1, 2, 3, 4, 5, 6,7, 8, 9, 10, and so on. A prime number is a number that only has two factors. Those factors are the number and one. A composite number has the numbers one and itself as its factors, as well as other numbers as its factors. Examples of a composite number are all numbers that end in 5, for they are all able to be divided by 5. Therefore, 15, 25, and 105 are all composite numbers. An example of a prime number is 9.