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Prime Factorization Calculator

Find all prime factors of a number with factor tree visualization and exponent notation.

Number & mode

Updates as you type
Mode
What do you want to do? ?
Number
Value ?
21k100k1M
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Factor table

PrimePowerExpressionValue

All divisors

Factor tree

Each branch splits to its smallest prime factor.

Formula

n = p1a1 · p2a2 · · pkak
n
The integer being factorized (≥ 2)
pi
A distinct prime factor of n
ai
The multiplicity of pᵢ (how many times it divides n)
τ(n)
Divisor count — (a₁+1)(a₂+1)…(aₖ+1)
σ(n)
Divisor sum — ∏ᵢ (pᵢ^(aᵢ+1)−1) / (pᵢ−1)
Worked example — your number
  1. Start with
  2. Trial-divide by primes 2, 3, 5, 7, … collecting each that divides in.
  3. Prime factors found:
  4. Factorization:
  5. τ = · σ =

The Fundamental Theorem of Arithmetic guarantees that every integer greater than 1 has exactly one prime factorization — up to the order of the factors. Trial division works well for the numbers in this tool; for very large integers, algorithms like Pollard's rho or the general number field sieve take over.

Examples