Factorials — What are Factorials?

Factorials

Factorial, in mathematics, is the product of all positive integers less than or equal to a given positive integer and denoted by that integer and an exclamation point.

Factorial Facts:

1. If you have the phone number 362–8800, your phone number is 10!.
2. As of right now, the phone number that corresponds to 13! does not exist. Go ahead, call it: 622–702–0800. (Turns out 622 as an area code isn’t used. Yet.).
3. 90! is the largest factorial you can tweet (it has 139 digits).
4. 200! has 375 digits. This is the same number of characters in the first paragraph of “Pride & Prejudice” by Jane Austen. The preamble to the U.S. Constitution is much shorter — it has only 327 characters!
5. Most students know that we can’t do 2.1! or (-3)! because factorials are limited to positive whole numbers. However, mathematicians have extended the application of factorial, called the Gamma function, into complex numbers (with the exception of negative integers). This application is often utilized in mathematical analysis and complex analysis.

Sources:

1. Wikipedia — Factorial
2. mathfour.com — Freaky Factorials and some Fun Facts that Follow