There are a few shortcomings here. One is that the calls to list() in #16 and #20 are unnecessary - strings are sequences in Python. Another is that the second solution for #19 isn't correct (it might output the right answer, but if so it's a fortunate accident).
ups thanx, forget to remove the list(str(x))-term.
And yes, the solution from #19 dont work in every century.