Factor 18 Digits 17.0 and Factor File Generator 17.0 are shareware
applications for the Macintosh.  

Factor 18 Digits lets the user factor integers of up to 18 decimal digits. 
It will also find random prime numbers and the next and previous prime
numbers from a given integer.  It uses the file from Factor File Generator
to do this.

After unstuffing the applications, run Factor File Generator and select
Help from the Apple menu for more info.