How is the simplest way to find prime numbers? - Answers

Try different numbers until you find one that is prime. A simple way (but not necessarily the fastest way) to check whether a candidate number is a Prime number is to check whether it is divisible by any number smaller than the number itself (and excluding 1). To make this somewhat faster, divide by 2, and then by all odd numbers, up to the square root of the number. For example, for numbers up to 100, you only need to test divisibility by 2, 3, 5, and 7. 9 is not a prime number, so you don't need to divide by 9; although according to the simple rule explained above, you would divide by 9, too. And 11 is greater than the square root of any number less than 100.