Determine if a number is Prime:

This Page presents the user with the chance to determine if a certain number is prime. The calculation is accurate up through a number 16 digits long.

Please enter a number and then press the Determine button:

Enter number here:

Check ALL Factors:  
Check This Many Factors:
Reset the Form:  

Result is:

Elapsed Time:

Algorithm Output:

As you read the result, remember the typical divisibility tests for numbers to diagnose if they are prime or not.

A Natural Number is Divisible by

2

If the Number is Even

3

If the Sum of the Digits is divisible by 3

4

If the last 2 digits is a number divisible by 4

5

If the last digit is 5 or 0

6

If the Number is even and divisible by 3

8

If the number is divisible by 4 and the result is even

9

If the sum of its digits is divisible by 9

10

If the last digit is 0

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