Prime Number Checker
Quickly verify if your number is prime — instant, accurate, effortless.
Enter any number below to check if it is a prime number. Our free online tool instantly determines whether the number is prime or not using fast algorithms.
What Is a Prime Number?
A prime number is a natural number greater than 1 that is divisible only by 1 and itself. The first few prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19...
Prime numbers are fundamental in number theory and have practical applications in areas such as encryption, algorithms, and data structures.
Why Use This Prime Checker?
- Quick results with no registration required
- Accurate prime checking for large numbers
- Perfect for homework, code validation, or curiosity
Related Prime Number Tools
Need more than just checking? Try our other tools:
- Prime Number Generator - Generate prime numbers between any two values.
- Prime Factor Calculator - Break down numbers into their prime factors.
How to Use the Prime Number Checker
This tool allows you to quickly check whether a number is a prime number or not. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.
- Enter any whole number greater than 1 into the input box.
- Click the "Check if Prime" button.
- The tool will instantly tell you whether the number is prime or not.
Example: Entering 17 will show that it is a prime number. Entering 20 will show that it is not.
FAQs About Prime Number Checking
You can divide the number by every integer from 2 up to its square root. If no divisions result in a whole number, it's prime. Or, just use this tool!
No. By definition, a prime number must have exactly two distinct positive divisors: 1 and itself. The number 1 only has one divisor.
No, prime numbers must be positive integers greater than 1.
Yes! All other even numbers are divisible by 2, so they're not prime.
Yes, our prime checker handles large integers quickly. Try entering values with 5, 6, or more digits!
Explore More
Continue exploring the world of prime numbers with our full Prime Number Calculator Suite.