2: Every exponential in the equation that the index number :4 have the remainder 1. So that every exponential in the equation has the same ending number, equals to:

\(\left(2+3+4+...+9\right)+199.\left(1+2+...+9\right)+1+2+3+4=9009.\)

So the last number of it is: 9

P/s: Vietnamese is permitted in Mathu.

Source: https://sites.google.com/site/toanhoctoantap/chuyen-dhe-toan-hoc/tim-chu