Check if a number is a prime or a composed number. List all prime numbers up to 10 000. If a number is prime, you can see all the prime divisors for it. Works with numbers up to 9223372036854775807. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number.