When is a file so large that it is no longer considered a number? If it is larger than 16 bytes?
If I remember correctly its also not so difficult to take an arbitrary zip file, append some noise so that it becomes prime (and will still decode). So even illegal primes are not difficult.
If I remember correctly its also not so difficult to take an arbitrary zip file, append some noise so that it becomes prime (and will still decode). So even illegal primes are not difficult.