Prime Number Checker

PRIME NUMBER CHECKER
A number is prime if it has exactly two factors ... 1 and itself.
For example, 17 is prime because its only factors are 1 and 17.
However, 35 is not prime, since it has factors 1, 35, as well as 5 and 7

The number 2 is prime, since its factors are 1 and 2 only.
The number 2 is the only even prime number. No other even number can be prime, because it will always have 2 as a factor.
For example, 4 isn't prime ... it's factors are 1, 4, and 2

Here are the first ten prime numbers:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ...
The 'prime' definition only applies to natural numbers, not to negative numbers or non-whole decimals.

It can sometimes be difficult to tell if a very large odd number is prime. For example, is 493 prime? The answer is no ... it has factors 1, 493, and also 17 and 29.

Included below is a handy prime number checker. Enter any number and press the 'calculate' button; it will tell you whether the number is prime or not. Give it a try ... enter 31,031 (don't use the comma). Jr. High Math | Science | Worsley School