IMO Shortlist 1991 problem 17
Dodao/la:
arhiva2. travnja 2012. Find the highest degree

of

for which

divides the number
%V0
Find the highest degree $k$ of $1991$ for which $1991^k$ divides the number $$1990^{1991^{1992}} + 1992^{1991^{1990}}.$$
Izvor: Međunarodna matematička olimpijada, shortlist 1991