6 min read
2026-02-07
The tool determines whether a number is prime, performs factorization, and finds prime numbers within a range.
A prime number is a natural number greater than 1 that is divisible only by 1 and itself. The first prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.
Primality check — determining whether a number is prime
Factorization — breaking a number into prime factors
Sieve of Eratosthenes — finding all prime numbers up to a given number
Nearest primes — finding prime numbers near a given number
Enter a number or range in the input field
Choose the operation: check, factorization, or range search
Click "Check"
Get the result with an explanation
To check primality, it is sufficient to test divisibility by all prime numbers up to the square root of the number being checked. If none divides it evenly, the number is prime.
Any composite number can be uniquely represented as a product of prime factors. For example: 360 = 2³ × 3² × 5.
See also: GCD and LCM, Factorials and Combinatorics, Roman Numerals