Calculating powmod...

[David Cleaver <wraithx@morpheus.net>]

Hello,

I'm interested in calculating "powmod"'s such as:
Mod(2^9182347891540, 9182347891541)
However, when I ran the function, it gave an error:
 ***   length (lg) overflow

Actually, I'm really interested to see if a number is a base 2 pseudoprime.  I 
saw the ispseudoprime function, but that uses the strong test, and I just need 
to know:
2^(n-1) == 1 (mod n)

I'm only going to be working with 64-bit inputs.  Is there some setting I need 
to change in pari to be able to find out the above?  Or is there some function I 
might have overlooked that performs that calculation?  Thanks for your time.

-David C.