The **`factorial()` function** returns the factorial of a positive integer.

> A **factorial** is a product of that positive integer and all the integers below it, until 1.

Figure 1 shows the mathematical representation of the `factorial()` function and the corresponding representation in Python.

> The `math` module is required for this function.

# Syntax
```python
factorial(integer)
```
# Parameter
This function requires a positive integer whose factorial is to be calculated.

# Return value
`factorial()` returns the factorial of the positive integer sent as a parameter.
> In the case of a `non-integral value`, an `error` is thrown.


# Example
The following example shows how we can use the `factorial()` function in Python.


#Module required
import math

#example
print ("factorial(6) : ", math.factorial(6))

print ("factorial(4) : ", math.factorial(4))

print ("factorial(0) : ", math.factorial(0))

What is math.factorial() in Python?

The factorial() function calculates the factorial of a positive integer using the math module.