Wondering if a number is prime? Here we give you the answer in seconds with our prime number checker. This is useful whether you’re working on math homework, programming, cryptography, or simply curious about numbers and their properties.
With our simple and accurate prime number checker, you can find out if any number is prime. Enter your number in the field below:
A prime number is a natural number greater than 1 that can only be divided by 1 and itself. This makes prime numbers the fundamental building blocks in our number system.
The first prime numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47
The number 2 is the only even number that is a prime number. All other prime numbers are odd numbers. There are infinitely many prime numbers. Some of the largest known prime numbers have millions of digits.
Our calculator uses an efficient algorithm to test if a number is prime.
The algorithm checks if the number can be divided by any other numbers than 1 and itself. Instead of testing all numbers, we only check up to the square root of the number, since factors come in pairs.
For odd numbers we only check odd divisors, which halves the number of tests. The algorithm handles special cases like 1 (not prime), 2 (only even prime) and negative numbers.
How large numbers can the calculator handle? The calculator works efficiently for numbers up to several million. For extremely large numbers the response may take a few seconds.
Why is 1 not a prime number? Although 1 can only be divided by itself, it is excluded from the prime number definition for mathematical reasons. This makes many theorems and algorithms simpler.
Are there patterns in prime numbers? While there is no simple formula to generate all prime numbers, there are interesting patterns such as twin primes (like 11 and 13) and prime gaps.
Can negative numbers be prime? No, prime numbers are defined as positive integers (natural numbers) greater than 1.
What is the largest known prime number? The largest known prime number is updated regularly. As of 2024 it has over 24 million digits and is a so-called Mersenne prime.
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