In Dementia2014/Mulfact how does one arrive at conclusion that that superfactorial(n)%329885391853=0 for all n>=999983

question link http://www.codechef.com/DMNT2014/problems/MULFACT. I got the concept(after the event :( ) but what I couldn't understand was as to how coders get to conclusion that after n=999983 all numbers will have their superfactorial == 0(mod 329885391853)

Thanks in advance