Prime Number Tester
Check if any number is prime instantly. Test single numbers, explore prime factorization, and find all primes in a range.
📐 Prime Factorization
🎯 Quick Test
Maximum range: 10,000
📊 Quick Presets
💡 How to Use This Tool
Test prime numbers in two ways:
Choose Mode
Select "Test Single Number" or "Find Primes in Range".
Enter Number(s)
Type a number to test or define a range.
View Results
See if it's prime and view factorization.
Copy Results
Copy the result to your clipboard.
📖 About Prime Number Tester
What is a Prime Number?
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. The first few prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29.
The Mathematical Definition
A number n is prime if:
- n > 1
- n is only divisible by 1 and n
Composite numbers are numbers greater than 1 that are not prime (they have additional factors).
Common Use Cases
- Cryptography: Prime numbers are fundamental to RSA encryption and secure communications
- Mathematics & Education: Learning about number theory and divisibility
- Programming: Implementing primality tests and factorization algorithms
- Competitive Programming: Solving algorithm challenges involving primes
- Data Science: Hash functions and random number generation
Primality Testing Methods
Trial Division
The simplest method: check if any number from 2 to √n divides n evenly.
Sieve of Eratosthenes
Efficient for finding all primes up to a given limit by iteratively marking composites.
Privacy & Security
All calculations happen locally in your browser using JavaScript. Your data never leaves your device - complete privacy guaranteed.