First, you can factor out 625 using the 'tree' method or the 'ladder' method.
625
/ \
5 125
/ \
5 25
/ \
5 5
This means you can say that 625=5 to the power of 4
If your problem requires you to use only whole integers with exponents, then that would be the only way.
If not, then you can also do 625=25*5²
