Prime Factorization Calculator

What is a prime number?

A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number.

Examples of prime numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97...

Examples of composite numbers: 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30...

The fundamental theorem of arithmetic states that every natural number greater than 1 can be written as a product of prime numbers in a unique way (up to the order of the factors). For example, 60 = 5 × 3 × 2 × 2.

What is prime factorization?

Prime factorization is the decomposition of a composite number into a product of prime numbers. There are several methods to find the prime factorization of a number.

Trial division

One method for finding the prime factorization of a composite number is trial division. Test integers by dividing the composite number by each integer until the result is no longer an integer.

Example: Prime factorization of 820

820 ÷ 2 = 410
410 ÷ 2 = 205
205 is not divisible by 2 or 3, but by 5: 205 ÷ 5 = 41
41 is a prime number.
Result: 820 = 41 × 5 × 2 × 2
or 820 = 41 × 5 × 2²

Prime decomposition (Factor tree)

Another method is to create a factor tree. Start by writing the number at the top, then break it down into factors. Continue breaking down composite factors until all factors are prime.

Example: Prime factorization of 820

Two different factor trees for 820:

Tree 1:
820 → 2 and 410
410 → 2 and 205
205 → 5 and 41
Tree 2:
820 → 20 and 41
20 → 4 and 5
4 → 2 and 2
Result: 820 = 41 × 5 × 2 × 2

Prime factorization of common numbers

Prime factorization of 2: prime number
Prime factorization of 3: prime number
Prime factorization of 4:
Prime factorization of 5: prime number
Prime factorization of 6: 2 × 3
Prime factorization of 7: prime number
Prime factorization of 8:
Prime factorization of 9:
Prime factorization of 10: 2 × 5
Prime factorization of 11: prime number
Prime factorization of 12: 2² × 3
Prime factorization of 13: prime number
Prime factorization of 14: 2 × 7
Prime factorization of 15: 3 × 5
Prime factorization of 16: 2⁴
Prime factorization of 17: prime number
Prime factorization of 18: 2 × 3²
Prime factorization of 19: prime number
Prime factorization of 20: 2² × 5
Prime factorization of 21: 3 × 7
Prime factorization of 22: 2 × 11
Prime factorization of 23: prime number
Prime factorization of 24: 2³ × 3
Prime factorization of 25:
Prime factorization of 26: 2 × 13
Prime factorization of 27:
Prime factorization of 28: 2² × 7
Prime factorization of 29: prime number
Prime factorization of 30: 2 × 3 × 5
Prime factorization of 32: 2⁵
Prime factorization of 36: 2² × 3²
Prime factorization of 40: 2³ × 5
Prime factorization of 42: 2 × 3 × 7
Prime factorization of 45: 3² × 5
Prime factorization of 48: 2⁴ × 3
Prime factorization of 50: 2 × 5²
Prime factorization of 54: 2 × 3³
Prime factorization of 60: 2² × 3 × 5
Prime factorization of 64: 2⁶
Prime factorization of 72: 2³ × 3²
Prime factorization of 75: 3 × 5²
Prime factorization of 80: 2⁴ × 5
Prime factorization of 81: 3⁴
Prime factorization of 84: 2² × 3 × 7
Prime factorization of 90: 2 × 3² × 5
Prime factorization of 96: 2⁵ × 3
Prime factorization of 100: 2² × 5²
Prime factorization of 101: prime number
Prime factorization of 102: 2 × 3 × 17
Prime factorization of 104: 2³ × 13
Prime factorization of 108: 2² × 3³
Prime factorization of 120: 2³ × 3 × 5
Prime factorization of 125:
Prime factorization of 128: 2⁷
Prime factorization of 135: 3³ × 5
Prime factorization of 144: 2⁴ × 3²
Prime factorization of 150: 2 × 3 × 5²
Prime factorization of 200: 2³ × 5²
Prime factorization of 300: 2² × 3 × 5²
Prime factorization of 400: 2⁴ × 5²
Prime factorization of 500: 2² × 5³
Prime factorization of 600: 2³ × 3 × 5²
Prime factorization of 700: 2² × 5² × 7
Prime factorization of 800: 2⁵ × 5²
Prime factorization of 900: 2² × 3² × 5²
Prime factorization of 1000: 2³ × 5³