Prime Number Checker to
Check if Numbers are Primes

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The prime number checker on this page will quickly check to see if a number is a prime (natural).

This free online calculator will let you know whether or not a given number is a prime -- with the click of a button.

Plus if it turns out the entry is not a natural number, the calculator will report the first divisor it found, as well as show the equation and the quotient.

If you would like to find all primes for a given composite, please visit the Prime Factorization Calculator.

Or, if you wish to generate a customizable, printable list of primes, please visit the primes list generator.

What Are Primes?

Primes, or natural numbers are any numbers that are greater than 1 that are only divisible by 1 and the numbers themselves. For example, 13 is a natural number because nothing other than 1 and itself can be divided evenly into 13.

The integer 14, on the other hand, is not a natural because it can be divided evenly by the factors 1, 2, 7, and 14 (see the Factoring Calculator to quickly find all factors of a number). The integer 14 and other non-primes are also referred to as composite numbers.

With that, let's use the Prime Number Checker to check see if a number is divisible by factors other than just 1 and itself.

Prime Number Checker
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Instructions: Enter the integer you want to check to see if it is a prime number, then click the "Prime Number Check" button.

Mouse over the blue question marks for a further explanation of each entry field. More in-depth explanations can be found in the glossary of terms located beneath the Prime Number Checker.

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Help Number to check if prime:
Help Is the entered number a prime (natural) number?
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Prime Number Calculator Glossary of Terms

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Prime Number: Also called a natural number, can be defined as any number greater than 1 that is only divisible by 1 and itself.

Number to check if prime: Enter a number that is greater than 1 that you want to perform a prime check on. Numbers greater than 1 million may cause the calculator to time out before it completes its calculations.

Is the entered number a prime (natural) number? This will be a yes or no result. Yes indicates the entry is prime, and No indicates the entry is not prime. If the answer is No, the calculator will report the first divisor it found.

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