Question 20
How many integers are factors of $2^{20}3^{23}$ but are not factors of $2^{10}3^{20}$?
Editorial convention: the supplied answer key uses positive factors, the usual contest convention; scoring here follows that convention. The signed-integer interpretation is discussed in the solution.
Editorial convention: the supplied answer key uses positive factors, the usual contest convention; scoring here follows that convention. The signed-integer interpretation is discussed in the solution.