*46*

# Extra Long Factorials in C

**Problem Statement:** The *factorial* of the integer n, written n!, is defined as:

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

Calculate and print the factorial of a given integer.

For example, if n = 30 , we calculate 30 x 29 x 28 x ………..x 3 x 2 x 1 and get.

2 6 5 2 5 2 8 5 9 8 1 2 1 9 1 0 5 8 6 3 6 3 0 8 4 8 0 0 0 0 0 0 0 in total 33 digits.

#### Note: Factorials of n > 20 can’t be stored even in a 64 – bit long variable. Big integers must be used for such calculations. Languages like Java, Python, Ruby etc. can handle big integers, but we need to write additional code in C/C++ to handle huge values.

**Description of program :** The below program can calculate factorial of any number, i.e. factorial of numbers above 20 which is not feasible for an 64 bit computer.

We have started with variable

**Output of above Code**

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