If u need to find the remainder the remainder , theres no need to evaluate 2^405 , this can be solved in the following ways.
2405 = (8)135=(7+1)135
Binomially expand the above expression as
= 135C07135+135C17134+135C27133+...+135C13471+135C13570
= In the above expansion, all the terms are divisible by 7 (They consist of 7 as a factor)
= Only 135C135 70 = 1 is non divisible as such 1 is the remainder
If you wanna find the quotient try logarithm
2405= antilog(405 log2) , it will give u a fair approx. values
Quotient = antilog(405*log2 - log7 )