so i have been given the key for the encryption of the message.
(e,n)= (13, 2747) as well as the encrypted message. (2206 0755 .....)
I have factored n = 67*41
and calculated phi(n)=66*40=2640.
I am having trouble decryypting the message because i cannot use a calculator to calculate
2206^(-203) mod n
The numbers are just too large.... (2437=-203= the inverse of 13 mod phi(n))
Is there an trick?