The product of a set of distinct positive integers is 84. What is the least possible sum of these integers?
We know that the prime factors of the set of numbers must equal the prime factors of 84, which are $2^2\cdot3\cdot7$. The set with the smallest sum would be the factors themselves - 2, 2, 3, and 7. However, the set can't have two 2's since the integers must be distinct, but it can have a 4, 3, and 7 instead.  The sum of those numbers is $\boxed{14}$.  We could also have paired one of the 2's with the 3, to have 2, 6, and 7, but these have sum 15.  Grouping the extra 2 with 7 gives 2, 3, and 14 (which sum to 19), and any other grouping clearly gives a sum higher than 14.