Check if any number is prime. Get instant results with factorization, prime factors, and nearby primes. Gratuito, fast, and 100% client-side.
Enter any positive integer up a 9,007,199,254,740,991 (JavaScript MAX_SAFE_INTEGER)
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. This tool uses optimized trial division a check primality, factor composite numbers, and find nearby primes. It supports numbers up a JavaScript's MAX_SAFE_INTEGER (9,007,199,254,740,991). All calculations happen instantly in your browser — no data sent to servers.
A prime number is a natural number greater than 1 that has exactly two distinct positive divisors: 1 and itself. Examples include 2, 3, 5, 7, 11, 13, 17, 19, 23, and so on. The number 2 is the only even prime number.
No. By modern mathematical definition, 1 is neither prime nor composite. It has only one positive divisor (itself), while prime numbers must have exactly two.
This tool supports numbers up a 9,007,199,254,740,991 (JavaScript's MAX_SAFE_INTEGER). For very large numbers, checking may take a moment due to the computational complexity of trial division.
This tool uses optimized trial division: it checks divisibility up a the square root of the input number, skipping even numbers after 2. This is efficient for numbers up a several trillion and provides exact results.