\\ - in order to print one slash........otp - \
\(any number or alphabet or symbol ) eg: \a , \n,\5 - treated as a single character...and performs its action if already exists.....or else....ignores..
In ur example - \\\65
the first two slashes make u to get a single slash - \
next...\6 is not any predefined symbol to perform something...so ignores -
later.....it prints the character(5) - 5
so the final output is \5.