What is 1 factorial ?

To find 1 factorial, or 1!, simply use the formula that multiplies the number 1 by all positive whole numbers less than it.

Let's look at how to calculate the Factorial of One :

  1! is exactly : 1

  Factorial of 1 can be calculated as:
1! = 1

  The number of trailing zeros in 1! is 0

  The number of digits in 1 factorial is 1.

• 0 Factorial
• Factorial of 2
• Factorial of 3
• Factorial of 4
• Factorial of 5

A factorial is showed by an integer and an exclamation symbol. In arithmetic, factorial is a multiplication procedure of natural numbers .

It multiplies the number by every natural number that is less than it .

Symbolically, it is represented as "!".

The function is used, among other things, to get the "n" way objects can be established .

To find the factorial of any given number, substitute the value for n in the given way :

n! = n × (n-1) × (n-2) × (n-3) × ….× 3 × 2 × 1

The expansion of the formula provides numbers to be replicated at the same time to obtain the factorial of the number.

We can also work out a factorial from the previous one. The factorial of any number is that number replicated the factorial of (that number minus 1).

So the rule is : n! = n × (n−1)!

Example :
1! Factorial = 1 = 1 × 0! = 1

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"

1) Can we have factorials for negative numbers ?
  Negative number factorials are undefined

2) What Is 0!
 Zero factorial or Factorial of 0 is simple, and its own value is equal to 1. So, 0! = 1.

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Factors of 1