Liouville proved the following property of the divisors of the divisors of a number:
1) Start with a number (e.g. 10)
2) Write down its divisors (1,2,5,10)
3) Write down the number of divisors of each divisor (1,2,2,4)
4) (1+2+2+4)²=81=1³+2³+2³+4³ pic.twitter.com/6YbXLdSszC

— Fermat's Library (@fermatslibrary) August 11, 2021