Who needs the system's default calculator anyway?

[TheKaneB]

Well, I like how you imposed yourself a set of limits, that's what sparks creativity in my opinion, and it's always more fun to code with limited resources (that's why I love retrocomputing as well).
That said, if I were you, I'd definitely implemented that thing in C++ with OpenMP. I bet I could reduce the run time from the 8h of the prime / shield to a few minutes on a modest quad core i5 pc