[cormacrelf]

There are a lot of easily describable primes, like the Mersenne primes. A lot of numbers can be described in fewer bits than directly. This is not always the case, but you could just keep looking for another more easily describable prime or broaden the search space to include non-destructive modifications of the data you're representing.

[mikeash]

This is just data compression. Most strings can’t be compressed, and nearly all strings can’t be compressed by more than a small amount.

[dorgo]

>nearly all strings can’t be compressed by more than a small amount.

source?

[mikeash]

https://en.m.wikipedia.org/wiki/Pigeonhole_principle

As you increase length, the number of possible strings grows exponentially. There are only a few (relatively) much smaller strings you can map to.