First, let's find all the factors of 81:
81/3=27
27/3=9
9/3=3
3/1=1
So the factors of 81 are 3,3,3,3, (the numbers by which we divided here).
This means we can write down 81 as 3*3*3*3 or [tex] 3^{4} [/tex] - which is the answer to the question! (three to the power of 4)