There’s a problem I solved awhile back which I was quite proud of:

Determine, with proof, the largest number that is the product of positive integers whose sum is 1976. (IMO 1976)

Note that this was at a high school olympiad level. Two days ago, my little brother brought me a state Mathcounts preparation packet. One of the problems was

Write 33 as the sum of two or more distinct prime numbers so that the product of these prime numbers is largest. What is the largest possible product?

While a proof is not needed, the move from an high school international level to a middle school state level in 40 years is pretty is pretty impressive.