?,432,902,008,176,640,000
This nineteen-digit integer shows the numerical value of
factorial 20. However, the leftmost digit has been omitted and
identifying it is this week's problem.
Factorial n (or n! as it is also known) equals the number of
different ways that n items can be arranged in a row. The actual
calculation is: 20x19x18x16x17... x5x4x3x2x1.
But there is no need to reach for your calculator! The missing
digit can be identified by other means, if you think carefully.
Find the solution online >>
