Q: What is the prime factorization of the number 21,867,520?

 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 5 x 4,271
    • or also written as { 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 5, 4,271 }
  • Written in exponential form: 210 x 51 x 4,2711

Why is the prime factorization of 21,867,520 written as 210 x 51 x 4,2711?

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 21,867,520

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 21,867,520 by 2

21,867,520 ÷ 2 = 10,933,760 - No remainder! 2 is one of the factors!
10,933,760 ÷ 2 = 5,466,880 - No remainder! 2 is one of the factors!
5,466,880 ÷ 2 = 2,733,440 - No remainder! 2 is one of the factors!
2,733,440 ÷ 2 = 1,366,720 - No remainder! 2 is one of the factors!
1,366,720 ÷ 2 = 683,360 - No remainder! 2 is one of the factors!
683,360 ÷ 2 = 341,680 - No remainder! 2 is one of the factors!
341,680 ÷ 2 = 170,840 - No remainder! 2 is one of the factors!
170,840 ÷ 2 = 85,420 - No remainder! 2 is one of the factors!
85,420 ÷ 2 = 42,710 - No remainder! 2 is one of the factors!
42,710 ÷ 2 = 21,355 - No remainder! 2 is one of the factors!
21,355 ÷ 2 = 10,677.5 - There is a remainder. We can't divide by 2 evenly anymore. Let's try the next prime number
21,355 ÷ 3 = 7,118.3333 - This has a remainder. 3 is not a factor.
21,355 ÷ 5 = 4,271 - No remainder! 5 is one of the factors!
4,271 ÷ 5 = 854.2 - There is a remainder. We can't divide by 5 evenly anymore. Let's try the next prime number
4,271 ÷ 7 = 610.1429 - This has a remainder. 7 is not a factor.
4,271 ÷ 11 = 388.2727 - This has a remainder. 11 is not a factor.
4,271 ÷ 13 = 328.5385 - This has a remainder. 13 is not a factor.
...
Keep trying increasingly larger numbers until you find one that divides evenly.
...
4,271 ÷ 4,271 = 1 - No remainder! 4,271 is one of the factors!

The orange divisor(s) above are the prime factors of the number 21,867,520. 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 5 x 4,271 = 21,867,520. It can also be written in exponential form as 210 x 51 x 4,2711.

Factor Tree

Another way to do prime factorization is to use a factor tree. Below is a factor tree for the number 21,867,520.

21,867,520
Factor Arrows
210,933,760
Factor Arrows
25,466,880
Factor Arrows
22,733,440
Factor Arrows
21,366,720
Factor Arrows
2683,360
Factor Arrows
2341,680
Factor Arrows
2170,840
Factor Arrows
285,420
Factor Arrows
242,710
Factor Arrows
221,355
Factor Arrows
54,271

More Prime Factorization Examples

21,867,51821,867,51921,867,52121,867,522
21 x 191 x 371 x 1031 x 151131 x 1,7871 x 4,0791131 x 431 x 39,119121 x 31 x 3,644,5871

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