Long ago, I had an idea of creating (actually, labeling) a clock that will have, instead of the numbers 1,…,12, important mathematical problems whose solution turned out to be that number. Such a clock could be awesome for mathematics departments.
This is a call for such problems. Please, consider posting problems for numbers that are not well-addressed yet.
These have some your numbers in them...
What do you get when you link primes, transcendentals, $0$, unity, subtraction, and equality? $$e^{2 \pi i}-1=0$$ A root inside a root inside a root... $$2=\sqrt{2\sqrt{2\sqrt{2\sqrt{2\sqrt{2\sqrt{2}}}}}}$$
What do you get when you sum all the natural numbers? Not what you think according to the Riemann zeta function. \begin{equation} 1+2+3+4...={-1 \over 12} \end{equation}