Prime Number Checker
Check whether any number is prime, find its prime factorisation, and get the next few prime numbers above it.
Prime Numbers Explained
What Makes a Number Prime?
A prime number has exactly two factors: 1 and itself. 2 is the only even prime. 1 is not prime (by definition, it has only one factor). The first ten primes are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.
Prime Factorisation
Every integer greater than 1 is either prime or can be expressed as a unique product of primes (Fundamental Theorem of Arithmetic). 84 = 2² × 3 × 7. This unique factorisation is the basis of the HCF and LCM methods.
Why Primes Matter
Modern internet security (RSA encryption) depends on the difficulty of factoring large numbers into primes. A public key uses two large primes multiplied together — finding those primes from the product takes longer than the age of the universe for sufficiently large numbers.
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