used to love playing this game in maths class where everyone would stand in a circle and then you would count, all in turn, so i say 1, the person next to me says 2 etc. but then if it's a square number you don't say it you just jump instead and if it's a prime number you put your hands on your head but don't say it and if it's square AND prime then you jump up with your hands on your head

can do the same thing with multiples of 3 and 5 as well. love maths fun.