> This page location: Math Functions > FACTORIAL
> Full Neon documentation index: https://neon.com/docs/llms.txt

# PostgreSQL FACTORIAL() Function

**Summary**: in this tutorial, you will learn how to use the PostgreSQL `factorial()` function to calculate the factorial of a number.

## Introduction to the PostgreSQL factorial() function

The factorial of a non-negative integer n is the product of all positive integers less than or equal to `n`:

```
n!=n×(n−1)×(n−2)×…×2×1
```

By convention, 0! = 1.

In PostgreSQL, you can use the built-in `factorial()` function to calculate the factorial of a number:

```sql
factorial(n)
```

In this syntax, `n` is the number that you want to calculate the factorial. The `factorial()` function returns null if n is null.

If n is negative, the factorial() function will issue an error:

```
ERROR:  factorial of a negative number is undefined
```

## PostgreSQL factorial() function example

Let's take some examples of using the `factorial()` function.

The following example uses the `factorial()` function to calculate the factorial of the number 10:

```sql
SELECT factorial(5);
```

Output:

```text
 factorial
-----------
       120
(1 row)
```

## Summary

- Use the `factorial()` function to calculate the factorial of a number.

---

## Related docs (Math Functions)

- [ABS](https://neon.com/postgresql/postgresql-math-functions/postgresql-abs)
- [CBRT](https://neon.com/postgresql/postgresql-math-functions/postgresql-cbrt)
- [CEIL](https://neon.com/postgresql/postgresql-math-functions/postgresql-ceil)
- [DEGREES](https://neon.com/postgresql/postgresql-math-functions/postgresql-degrees)
- [DIV](https://neon.com/postgresql/postgresql-math-functions/postgresql-div)
- [EXP](https://neon.com/postgresql/postgresql-math-functions/postgresql-exp)
- [FLOOR](https://neon.com/postgresql/postgresql-math-functions/postgresql-floor)
- [GCD](https://neon.com/postgresql/postgresql-math-functions/postgresql-gcd)
- [LCM](https://neon.com/postgresql/postgresql-math-functions/postgresql-lcm)
- [LN](https://neon.com/postgresql/postgresql-math-functions/postgresql-ln)
- [LOG](https://neon.com/postgresql/postgresql-math-functions/postgresql-log)
- [MOD](https://neon.com/postgresql/postgresql-math-functions/postgresql-mod)
- [MIN_SCALE](https://neon.com/postgresql/postgresql-math-functions/postgresql-min_scale)
- [PI](https://neon.com/postgresql/postgresql-math-functions/postgresql-pi-function)
- [POWER](https://neon.com/postgresql/postgresql-math-functions/postgresql-power)
- [RADIANS](https://neon.com/postgresql/postgresql-math-functions/postgresql-radians)
- [RANDOM](https://neon.com/postgresql/postgresql-math-functions/postgresql-random)
- [ROUND](https://neon.com/postgresql/postgresql-math-functions/postgresql-round)
- [SCALE](https://neon.com/postgresql/postgresql-math-functions/postgresql-scale)
- [SIGN](https://neon.com/postgresql/postgresql-math-functions/postgresql-sign)
- [SQRT](https://neon.com/postgresql/postgresql-math-functions/postgresql-sqrt)
- [TRIM_SCALE](https://neon.com/postgresql/postgresql-math-functions/postgresql-trim_scale)
- [TRUNC](https://neon.com/postgresql/postgresql-math-functions/postgresql-trunc)
- [WIDTH_BUCKET](https://neon.com/postgresql/postgresql-math-functions/postgresql-width_bucket)