We play with  numbers with at least 20 decimal places here.
If you could make one Giga (10^9) guesses per second, it would take:

10^20 / 10^9 = 10^11 seconds

This is equivalent to roughly 3.2 million years. So, even with an incredibly fast computer making a Giga guesses per second, it would take millions of years to guess a 20-decimal-place number.

We'd better start practicing crystal ball gazing to guess what the correct range of Puzzle 66 is