How many people like Richard Arenstorf worked on the Apollo project? Tens? Hundreds? Thousands? Myriads? How many equally hard problems in cryogenic zero-gee p

How many people like Richard Arenstorf worked on the Apollo project? Tens? Hundreds? Thousands? Myriads? How many equally hard problems in cryogenic zero-gee pumping, combustion dynamics, space suit design, telemetry, computer hardware, etc. were there? Were there no harder problems solved that deserve more public acclaim? 'Showing a person "thinking" or writing equations is not telegenic.' Somehow Einstein, Feynman, and Hawking are all pop culture figures, so it can't simply be that.