Hope you can help me solving a peculiar problem or at least giving me a hint about how it could be solved.
I'd like to know if it does exist a mathematical function that is able to reduce any large number (about 50 or 100 digits long) to a small number, i.e. something like an "inverted" factorial.
When I'm talking of large or small numbers, I talk about the amount of digits needed to represent it, i.e. 2500 is smaller than 3,1415 because the first requires 4 digits, while the latter requires 5 digits (the comma is insignificant).
Btw, the function should also be reversible (I need to convert the large number to a small one and vice versa).
Thank you in advance.
Best regards,

Stephen Thorne