RosettaCodeData/Task/Increment-a-numerical-string/LaTeX/increment-a-numerical-string.tex

\documentclass{minimal}
\newcounter{tmpnum}
\newcommand{\stringinc}[1]{%
    \setcounter{tmpnum}{#1}%
    \stepcounter{tmpnum}%
    \arabic{tmpnum}%
}
\begin{document}
The number 12345 is followed by \stringinc{12345}.
\end{document}