How to calculate the factorial of 21
To find 21 factorial, or 21!, simply use the formula that multiplies the number 21 by all positive whole numbers less than it.
Let's look at how to calculate the Factorial of Twenty-one :
21! is exactly : 51090942171709440000
Factorial of 21 can be calculated as:
21! = 21 x 20 x 19 x 18 x ... x 3 x 2 x 1
The number of trailing zeros in 21! is 4
The number of digits in 21 factorial is 20.
Factorials of Numbers similar to 21
What Is Factorial?
A factorial is represented by an integer and an exclamation mark. In math concepts, factorial is a multiplication function of natural numbers .
It multiplies the number by every noreal number that is less than it .
Symbolically, it is listed as "!".
The function is used, among other things, to get the "n" way elements can be arranged .
To find the factorial of any given number, replace the value for n in the given solution :
n! = n × (n-1) × (n-2) × (n-3) × ….× 3 × 2 × 1
The expansion of the formula provides the numbers to be replicated with each other to get the factorial of the number.
We can also calculate a factorial from the previous one. The factorial of any number is that number times the factorial of (that number minus 1).
So the rule is : n! = n × (n−1)!
21! Factorial = 21 x 20 x 19 x 18 x ... x 3 x 2 x 1 = 21 × 20! = 51090942171709440000
What are Factorials Used For?
The best use of factorial is in Combinations and Permutations.
Example : Determine how to arrange letters without repeating?
There one way for 1 letter "a":
2 ways for two letters "ab": ab, ba.
There are 6 ways for 3 letters "abc": abc acb cab bac bca.
There are 24 ways for 1234 of the letters "abcd"
Frequently Asked Questions on Factorial
1) Can we have factorials for negative numbers ?
Negative integer factorials are undefined
2) What Is 0!
Zero factorial or Factorial of 0 is simple, and its value is equal to 1. So, 0! = 1.