Factorial calculator
The number of ways to shuffle a deck of cards is 52!, roughly 8 × 10⁶⁷. That is more than the estimated number of atoms in our galaxy. Every properly shuffled deck in history has almost certainly been in an order never seen before and never to be seen again — which is the most vivid demonstration of factorial growth anyone has come up with.
A factorial is every whole number up to n multiplied together. 10! is 3,628,800. Growth is extraordinarily fast — 20! already exceeds two quintillion, and 52! is about 8 × 10⁶⁷.
How to calculate a factorial
Zero factorial is defined as one, which looks arbitrary and is not. It falls out of the definition n! = n × (n−1)!: applying it at n = 1 gives 1! = 1 × 0!, so 0! must be 1. It is also what makes the combination formula work — C(n,n) should be 1, meaning there is exactly one way to choose everything, and that only comes out right if 0! = 1.
Questions
3,628,800.