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:
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
If the Number is Even
If the Sum of the Digits is divisible by 3
If the last 2 digits is a number divisible by 4
If the last digit is 5 or 0
If the Number is even and divisible by 3
If the number is divisible by 4 and the result is
If the sum of its digits is divisible by 9
If the last digit is 0