Q: What is the prime factorization of the number 123,904?

 A:
  • The prime factors are: 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 11 x 11
    • or also written as { 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 11, 11 }
  • Written in exponential form: 210 x 112

Why is the prime factorization of 123,904 written as 210 x 112?

What is prime factorization?

Prime factorization or prime factor decomposition is the process of finding which prime numbers can be multiplied together to make the original number.

Finding the prime factors of 123,904

To find the prime factors, you start by dividing the number by the first prime number, which is 2. If there is not a remainder, meaning you can divide evenly, then 2 is a factor of the number. Continue dividing by 2 until you cannot divide evenly anymore. Write down how many 2's you were able to divide by evenly. Now try dividing by the next prime factor, which is 3. The goal is to get to a quotient of 1.

If it doesn't make sense yet, let's try it...

Here are the first several prime factors: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29...

Let's start by dividing 123,904 by 2

123,904 ÷ 2 = 61,952 - No remainder! 2 is one of the factors!
61,952 ÷ 2 = 30,976 - No remainder! 2 is one of the factors!
30,976 ÷ 2 = 15,488 - No remainder! 2 is one of the factors!
15,488 ÷ 2 = 7,744 - No remainder! 2 is one of the factors!
7,744 ÷ 2 = 3,872 - No remainder! 2 is one of the factors!
3,872 ÷ 2 = 1,936 - No remainder! 2 is one of the factors!
1,936 ÷ 2 = 968 - No remainder! 2 is one of the factors!
968 ÷ 2 = 484 - No remainder! 2 is one of the factors!
484 ÷ 2 = 242 - No remainder! 2 is one of the factors!
242 ÷ 2 = 121 - No remainder! 2 is one of the factors!
121 ÷ 2 = 60.5 - There is a remainder. We can't divide by 2 evenly anymore. Let's try the next prime number
121 ÷ 3 = 40.3333 - This has a remainder. 3 is not a factor.
121 ÷ 5 = 24.2 - This has a remainder. 5 is not a factor.
121 ÷ 7 = 17.2857 - This has a remainder. 7 is not a factor.
121 ÷ 11 = 11 - No remainder! 11 is one of the factors!
11 ÷ 11 = 1 - No remainder! 11 is one of the factors!

The orange divisor(s) above are the prime factors of the number 123,904. If we put all of it together we have the factors 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 11 x 11 = 123,904. It can also be written in exponential form as 210 x 112.

Factor Tree

Another way to do prime factorization is to use a factor tree. Below is a factor tree for the number 123,904.

123,904
Factor Arrows
261,952
Factor Arrows
230,976
Factor Arrows
215,488
Factor Arrows
27,744
Factor Arrows
23,872
Factor Arrows
21,936
Factor Arrows
2968
Factor Arrows
2484
Factor Arrows
2242
Factor Arrows
2121
Factor Arrows
1111

More Prime Factorization Examples

123,902123,903123,905123,906
21 x 411 x 1,511133 x 131 x 353151 x 24,781121 x 31 x 1071 x 1931

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