Free Online Calculator

Prime Factorization Calculator

Break a number into its prime factors.

Last updated: Free, no sign-up Private — runs in your browser

Quick answer: prime factorization

Divide repeatedly by the smallest prime that fits until you reach 1. 360 = 2³ × 3² × 5.

Overview of the Prime Factorization Calculator

Every whole number greater than 1 is either prime or can be written as a product of primes in exactly one way. This calculator finds that factorization for any number up to a quadrillion, shows it in exponent form, lists the division steps, says whether the number is prime and gives the number and sum of its divisors.

Prime factors are the basis of the GCF and LCM. See the Factor Calculator, GCF Calculator and LCM Calculator; for huge integers try the Big Number Calculator.

How We Calculate

The calculator applies the standard method step by step.

  1. Divide the number by 2 as many times as possible, then by 3, then by 5, 7, 11 and so on.
  2. Stop when the remaining number is 1, or when the next prime squared exceeds it (then it is prime).
  3. Write the primes with exponents for repeats.
  4. Number of divisors = product of (exponent + 1); sum of divisors uses the geometric series for each prime.
n = p₁^a₁ × p₂^a₂ × … × pₖ^aₖ   divisors = (a₁ + 1)(a₂ + 1)…(aₖ + 1)
Worked example — prime factorization calculator
ItemValue
Prime factors (with repeats)2 × 2 × 2 × 3 × 3 × 5
Exponent form2³ × 3² × 5
Distinct primes3
Total prime factors6
Number of divisors24
Sum of divisors1,170
Prime?No — composite
Division steps
Divide by the next primeQuotient
360 ÷ 2180
180 ÷ 290
90 ÷ 245
45 ÷ 315
15 ÷ 35
5 ÷ 51
Prime factorization of different numbers
NumberPrime factors
602² × 3 × 5
3602³ × 3² × 5
10017 × 11 × 13
10242¹⁰
1234562⁶ × 3 × 643
Prime numbers up to 100
RangePrimes
1–252, 3, 5, 7, 11, 13, 17, 19, 23
26–5029, 31, 37, 41, 43, 47
51–7553, 59, 61, 67, 71, 73
76–10079, 83, 89, 97

Prime Factorization Calculator — Frequently Asked Questions

What is prime factorization?

Writing a number as a product of prime numbers, such as 360 = 2³ × 3² × 5.

Is the prime factorization of a number unique?

Yes — by the Fundamental Theorem of Arithmetic, apart from the order of the factors.

How do I use a factor tree?

Split the number into any two factors, then keep splitting each factor until every branch ends in a prime.

How do I know if a number is prime?

If no prime up to its square root divides it, it is prime. The calculator reports it directly.

What is the largest number this can factor?

Up to 10¹⁵ (one quadrillion), instantly in your browser.

Why is prime factorization important?

It underlies fractions, GCF and LCM, and the security of RSA encryption depends on how hard it is to factor very large numbers.

How is the prime factorization calculator calculated?

It uses the standard method: n = p₁^a₁ × p₂^a₂ × … × pₖ^aₖ   divisors = (a₁ + 1)(a₂ + 1)…(aₖ + 1) The full working and a worked example are shown on this page.

How accurate is this calculator?

Decimal results use standard double-precision arithmetic (about 15–16 significant digits). Tools that work with whole numbers — big numbers, factors, bases, combinations — use exact integer arithmetic, so no digits are lost.

Can I use it for homework or exams?

Yes for checking your work and learning the method. The steps and formula are shown so you can understand the answer, but follow your teacher's rules about calculators in exams.

Is my data stored?

No. Everything is calculated in your browser and nothing you enter is uploaded or saved.

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