Prime Number Checker
Check if a number is prime, and break any number down into its prime factors.
Show solution steps
What is the Prime Number Checker?
A prime number is a whole number greater than 1 with no divisors other than 1 and itself. Every other whole number can be written as a product of primes — its prime factorization.
How to Calculate
The checker tests divisibility up to the square root of the number; the factorization repeatedly divides out the smallest prime factor.
Formula
Prime if divisible only by 1 and itself.
How to Use
- Enter your details in the fields above.
- The result updates instantly as you type.
- Use Copy, Print or Download PDF to save your result.
Frequently Asked Questions
Why only check up to the square root?
If a number has a factor larger than its square root, it must also have a matching factor smaller than it u2014 so checking up to the square root is enough.
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