I got an entirely different error when I did a sqrt($N) before factoring:

  DB<1> n
main::(factsqrt.pl:5):    my $N = $_;
  DB<1> n
main::(factsqrt.pl:6):    my $sqrt2 = sqrt($N);
  DB<1> n
main::(factsqrt.pl:7):    my $a = factorint($N);
  DB<1> n
  DB<1> p $a
Mat([-1,1])
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However, this is not a bug in Math::Pari, but a side effect of perl's conversion of string to numbers.

The number "24777695232" first comes in as a string from the command line. Applying the function "sqrt" to it converts it to a double. When you pass it to Math::Pari, it goes in as a double. Naturally, the module fails to do the right thing. If you call a Math::Pari function first, like factorint, it automatically converts the string into a long Pari integer and operates on that.