Q: What is the prime factorization of the number 221,900?

 A:
  • The prime factors are: 2 x 2 x 5 x 5 x 7 x 317
    • or also written as { 2, 2, 5, 5, 7, 317 }
  • Written in exponential form: 22 x 52 x 71 x 3171

Why is the prime factorization of 221,900 written as 22 x 52 x 71 x 3171?

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 221,900

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 221,900 by 2

221,900 ÷ 2 = 110,950 - No remainder! 2 is one of the factors!
110,950 ÷ 2 = 55,475 - No remainder! 2 is one of the factors!
55,475 ÷ 2 = 27,737.5 - There is a remainder. We can't divide by 2 evenly anymore. Let's try the next prime number
55,475 ÷ 3 = 18,491.6667 - This has a remainder. 3 is not a factor.
55,475 ÷ 5 = 11,095 - No remainder! 5 is one of the factors!
11,095 ÷ 5 = 2,219 - No remainder! 5 is one of the factors!
2,219 ÷ 5 = 443.8 - There is a remainder. We can't divide by 5 evenly anymore. Let's try the next prime number
2,219 ÷ 7 = 317 - No remainder! 7 is one of the factors!
317 ÷ 7 = 45.2857 - There is a remainder. We can't divide by 7 evenly anymore. Let's try the next prime number
317 ÷ 11 = 28.8182 - This has a remainder. 11 is not a factor.
317 ÷ 13 = 24.3846 - This has a remainder. 13 is not a factor.
317 ÷ 17 = 18.6471 - This has a remainder. 17 is not a factor.
...
Keep trying increasingly larger numbers until you find one that divides evenly.
...
317 ÷ 317 = 1 - No remainder! 317 is one of the factors!

The orange divisor(s) above are the prime factors of the number 221,900. If we put all of it together we have the factors 2 x 2 x 5 x 5 x 7 x 317 = 221,900. It can also be written in exponential form as 22 x 52 x 71 x 3171.

Factor Tree

Another way to do prime factorization is to use a factor tree. Below is a factor tree for the number 221,900.

221,900
Factor Arrows
2110,950
Factor Arrows
255,475
Factor Arrows
511,095
Factor Arrows
52,219
Factor Arrows
7317

More Prime Factorization Examples

221,898221,899221,901221,902
21 x 31 x 311 x 1,1931591 x 3,761131 x 171 x 191 x 229121 x 110,9511

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