Sure.

1. Build factor pair so large it takes all atoms in the universe to store it.

2. Since there's no room for anything else, nothing can factor it.

:^)

In reality you can't get past a 2^256 limit of dev/urandom cspring without introducing your own random number generator which is possible.

But yeah its easy math, lets say the pair is 1,000,000. Thats 1,000,000! possible combinations. You could stack 1,000,000 PB drives across the universe and not be able to store all the unique combinations.