Prime Factor Calculator

What this calculator does

Prime factorisation rewrites a whole number as a product of prime numbers. It is useful for simplifying fractions, finding common factors and understanding divisibility.

Formula used

The calculator repeatedly divides the number by the smallest prime factor available until only prime factors remain.

How to read the result

The factor list multiplied together gives the original number. Repeated factors are shown more than once.

Assumptions

• Uses whole numbers greater than 1.
• Rounds the input down to an integer.
• Very large numbers can be slower to factor.

Sources and checks

This calculator uses a standard public formula. Where rules or thresholds can change, source links are listed on the relevant page.

Frequently asked questions