%%
%% The LaTeX Companion, 3ed
%%
%% Example 13-3-23 on page II-318 in "Numbering".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{111.0pt}

  \setlength\parskip{1pt}   % example looks a bit odd otherwise in short measure

%StartShownPreambleCommands
\usepackage{garamondlibre} \linespread{1.1}
\usepackage[english,greek]{babel}
\newcommand\eng[1]{\foreignlanguage{english}{#1}}
%StopShownPreambleCommands

\begin{document}
123456 \eng{in Greek notation:} \greeknumeral{123456} \par
987654 \eng{in Greek notation:} \Greeknumeral{987654}
\end{document}