Given an integer $$$N$$$, how many of its divisors are also divisors of $$$N - 1$$$?
For Chinese readers, Chinese statement is here:
Chinese Statement
Someone says it's related to the theoretical proof of the $$$abc$$$ conjecture, but I simply cannot understand why...
1
$$$gcd(x,x-1)=gcd(x-1,x-x+1)=gcd(x-1,1)=1$$$
:D
Your chinese statement is crap. Are you trolling or what?