How many different ways can you arrange the numbers 1 to 20?

Answer 1

You can arrange them in (20 x 19 x 18 x 17 x 16 x ..... 4 x 3 x 2) ways.

That number is called "20 factorial", and written " 20! ".

It's a big number ... bigger than my calculator can show exactly.

Rounded to the nearest billion, it's

2,432,902,008,000,000,000