Question

What is 9^21 can somebody please help me

Answer 1

It is 9*9 21 times so 
9*9*9*9*9*9*9*9*9*9*9*9*9*9*9*9*9*9*9*9*9=

1.09418989e20 is the answer.

Answer 2

Extract Form: 1094189131512000000
Decimal Form: 1.09418989 * $10^{20}$