Skip to main content

### Factorial

The factorial function (symbol: !) says to multiply all whole numbers from our chosen number down to 1.

Examples:

• 4! = 4 × 3 × 2 × 1 = 24
• 7! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040
• 1! = 1

#### PHP: using gmp_fact function

A native PHP function called gmp_fact is available and it calculates the factorial of a number:

`echo gmp_fact(5);`

#### PHP: creating a recursive function

`// Formula: n! = n*(n-1)*(n-2)*(n-3)...3.2.1 and zero factorial is defined as one i.e. 0! = 1.function factorial(\$n){    if (\$n == 0)        return 1;    else        return(\$n * factorial(\$n - 1));}echo factorial(5);`

#### JAVA: simple for cycle

`class Factorial {    public static void main(String args[]){          int i,fact=1;        int number=5;// It is the number to calculate factorial        for(i=1; i<=number; i++) {            fact=fact*i;        }        System.out.println("Factorial of "+number+" is: "+fact);        }}`

#### Javascript recursive function

`var f = [];function factorial (n) {  if (n == 0 || n == 1)    return 1;  if (f[n] > 0)    return f[n];  return f[n] = factorial(n-1) * n;}console.log( factorial(4) ); // 24`