Q: What is the prime factorization of the number 15,391?

 A:
  • The prime factors are: 15,391
    • or also written as { 15,391 }
  • Written in exponential form: 15,3911

Why is the prime factorization of 15,391 written as 15,3911?

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 15,391

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 15,391 by 2

15,391 ÷ 2 = 7,695.5 - This has a remainder. Let's try another prime number.
15,391 ÷ 3 = 5,130.3333 - This has a remainder. Let's try another prime number.
15,391 ÷ 5 = 3,078.2 - This has a remainder. Let's try another prime number.
...
Keep trying increasingly larger numbers until you find one that divides evenly.
...
15,391 ÷ 15,391 = 1 - No remainder! 15,391 is one of the factors!

The orange divisor(s) above are the prime factors of the number 15,391. If we put all of it together we have the factors 15,391 = 15,391. It can also be written in exponential form as 15,3911.

Factor Tree

Another way to do prime factorization is to use a factor tree. Below is a factor tree for the number 15,391.

More Prime Factorization Examples

15,38915,39015,39215,393
111 x 1,399121 x 34 x 51 x 19125 x 131 x 37131 x 71 x 7331

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