if you're writing the formulae longhand, SUBTOTAL() can be made to ignore or include hidden values;
just add 100 to the aggregate function
so if you want to count just visible numeric cells, use SUBTOTAL(103,ranges) [unless you've used autofilter, in which case values hidden by this will always be ignored]

it's also worth noting that SUBTOTAL() ignores any nested subtotals in its specified ranges (so no double counting)

and finally, if you're having trouble remembering the order of aggregate fucntions, they're alphabetical (took me ages to spot that one! - only when i wrote out a crib list that i noticed it)