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Prime Factorization Calculator

Check if a number is prime and find its prime factors, all divisors and their sum.

Runs instantly in your browser — results update as you type.

How do you find the prime factors of a number?

Divide the number by the smallest prime that divides it, repeat with the result, and continue until you reach 1. For example, 360 = 2 × 2 × 2 × 3 × 3 × 5 = 2³ × 3² × 5, which has (3+1)(2+1)(1+1) = 24 divisors.

What you get

  • Prime or composite, with the factorization in exponent form.
  • The number of divisors and their sum, and the full divisor list (up to 400).
  • Whether the number is a perfect square or a perfect number (like 28 = 1 + 2 + 4 + 7 + 14).

Frequently asked questions

Is 1 a prime number?

No. A prime has exactly two divisors, 1 and itself.

What is the largest number I can check?

10^15 (one quadrillion).

Why is factorization unique?

The fundamental theorem of arithmetic: every integer above 1 has exactly one prime factorization.