Prime numbers are numbers that have no divisors. Think of 7 peas, you can't divide them into equal portions, therefore 7 is prime.
More precisely, prime numbers are natural numbers greater than 1 that have no positive divisors other than 1 and themselves.
This program computes all prime numbers between 0 and N (by the method of 'Eratosthenes' sieve').
Be aware of time consumption and RAM requirements for higher values of N. Some browsers limit script running time!