Pretend the $20 million is guaranteed, and if anything will increase slightly over time.
What problems could be significantly improved for $20 million?
(I am dreaming of winning the $1.55 billion Powerball drawling. Then taking the lumpsum, posting taxes, investing, and spending 4% each and every year. I understand that the actual may be more, or less than the started amount.)
Throw as much money as possible into the best institutes for cancer research in the world, until cancer is cured.
Then, for myself, commission the best architects and contractors to have an absolutely exact replica of the Spencer Mansion built for me.