A prime number is a natural number greater than 1 that has only two factors, 1 and itself. In other words, it is a positive integer that is divisible by only 1 and the number itself. For example, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, and 97 are the first 25 prime numbers. A natural number greater than 1 that is not prime is called a composite number. Prime numbers are important in number theory and mathematics in general because of the fundamental theorem of arithmetic, which states that every integer larger than 1 can be written as a product of one or more primes.