Prime Factors

A prime is a whole number above 1 that only 1 and itself go into, like 2, 3, 5, 7 and 11. Every whole number above 1 is a product of primes in exactly one way, and that product is its prime factorization: 360 = 2 × 2 × 2 × 3 × 3 × 5, or 2³ × 3² × 5 with powers.

The factor tree splits the number by its smallest prime, again and again, until only a prime is left. The circled primes are the factors. To count the divisors, add 1 to each power and multiply: (3 + 1) × (2 + 1) × (1 + 1) = 24 for 360.

Type a second number to find the greatest common factor (GCF: each shared prime at its lower power) and the least common multiple (LCM: every prime at its higher power). Two numbers whose GCF is 1 are coprime. 0 and 1 have no prime factors.

Numbers up to 15 digits are exact. Small primes are tried first, then a fast method called Pollard's rho splits what is left. Your numbers are saved on this device only. Clear all empties them, and Undo brings them back.