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?