How to use Prime Number Checker
- Enter a whole number.
- Read whether it is prime.
- See the prime factors and the next and previous prime.
About this tool
A prime number has exactly two divisors: 1 and itself. The checker tests divisibility up to the square root of the number, which is fast enough for values up to about 10^15. Composite numbers are broken into prime factors, such as 360 = 2^3 x 3^2 x 5.
The number 1 is not prime, and 2 is the only even prime.
Frequently Asked Questions
- Is 1 a prime number?
- No. Primes must have exactly two distinct divisors, and 1 has only one.
- What is the largest number I can check?
- This tool accepts values up to 1,000,000,000,000,000 (10^15).
Related tools
- GCD and LCM CalculatorEnter a list of whole numbers to find their greatest common divisor and least common multiple.
- Fibonacci CalculatorGet any Fibonacci number up to the 5000th, and list the start of the sequence.
- Circle CalculatorEnter one measurement of a circle and get all the others.
- Rectangle CalculatorEnter the length and width to get area, perimeter and diagonal.
- Triangle CalculatorEnter three side lengths to get the area, perimeter and all three angles.
- Average CalculatorPaste a list of numbers to get the mean, median, mode and more.