# How's It Possible?

You have a set of 20 different objects.

Let $$S$$ be the total number of ways in which you can select and permute any number of these objects.

Find the digit sum of $$S$$.

Details and Assumptions

• The digit sum of a number is the sum of its individual digits. For example, the digit sum of 121 is $$1+2+1 = 4$$.
• You can pick any number of objects, from 0 to 20.
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