\documentclass[a4paper]{article}
\usepackage{pstricks}
\usepackage{pst-node}
\makeatletter
\def\tcircled#1{%
	\leavevmode\hbox{\setbox0=\hbox{#1}\relax
	\dimen0=\the\wd0\dimen1=\the\ht0
	\ifdim\dimen0>\dimen1\dimen2=\dimen0\else\dimen2=\dimen1\fi
	\divide\dimen0 by 2\divide\dimen1 by 2\advance\dimen2 by 5pt
	\put(\strip@pt\dimen0, \strip@pt\dimen1){\circle{\strip@pt\dimen2}}
	\box0}%
}
\def\tcircledI#1{{%
	\psset{unit=1pt}
	\setbox0=\hbox{#1}\relax
	\dimen0=\the\wd0\dimen1=\the\ht0
	\divide\dimen0 by 2\divide\dimen1 by 2
	\ifdim\dimen0>\dimen1\dimen2=\dimen0\else\dimen2=\dimen1\fi
	\advance\dimen2 by +5pt
	\rput(\dimen0, \dimen1){\pscircle{\dimen2}}
	\box0%
}}
\def\tcircleII#1{%
	\ensuremath{\mathbin{\settowidth{\dimen7}{\mbox{$\bigcirc$}}%
              \makebox[0pt][l]{$\bigcirc$}\makebox[\dimen7]{#1}}}}

\def\tcircledIII#1{\circlenode{@dummy}{#1}}%
\makeatother
\parindent=0pt
\begin{document}
\section*{with \LaTeX}

\verb+\textcircled{$\phi$}+ \textcircled{$\phi$}


\verb+\tcircled{1}\quad \tcircled{16}\quad \tcircled{1999}\quad \tcircled{999 999}+

\tcircled{1}\quad \tcircled{16}\quad \tcircled{1999}\quad \tcircled{999 999}

\verb+\tcircleII{$\phi$}+ \tcircleII{$\phi$}+

\tcircleII{$\phi$}+ \tcircleII{$\phi$}

\Huge
{\normalsize\verb+\textcircled{$\phi$}+} \textcircled{$\phi$}

\tcircled{1}\quad \tcircled{16}\quad \tcircled{1999}\quad \tcircled{999 999}

{\normalsize\verb+\tcircleII{$\phi$}+} \tcircleII{$\phi$}

\normalsize
\section*{with PSTricks}
\tcircledI{1}\quad \tcircledI{16}\quad \tcircledI{1999}\quad \tcircledI{999 999}

\vspace{1cm}\Huge
\tcircledI{1}\quad \tcircledI{16}\quad \tcircledI{1999}\quad \tcircledI{999 999}

\normalsize
\section*{with PST-node}
\tcircledIII{1}\quad \tcircledIII{16}\quad \tcircledIII{1999}\quad \tcircledIII{999 999}

\Huge
\tcircledIII{1}\quad \tcircledIII{16}\quad \tcircledIII{1999}\quad \tcircledIII{999 999}

\end{document}