A white number inside a black circle.

Created from this answer linked in the question above.

\documentclass{article}
\usepackage{tikz}
\usepackage{xcolor}
\newcommand*\circled[1]{\tikz[baseline=(char.base)]{
            \node[shape=circle,fill,inner sep=2pt] (char) {\textcolor{white}{#1}};}}

\begin{document}
\circled{1}
\end{document}

In what context do you want to use the numbers?

This does work in many situations. Observe that the color of the number and the circle are chosen automatically.

\documentclass{memoir}
\usepackage{tikz}
\newcommand{\ballnumber}[1]{\tikz[baseline=(myanchor.base)] \node[circle,fill=.,inner sep=1pt] (myanchor) {\color{-.}\bfseries\footnotesize #1};}

\begin{document}
Earum excepturi inventore necessitatibus aliquid reiciendis enim.  \ballnumber{37} Earum excepturi inventore necessitatibus aliquid reiciendis enim.
\end{document}

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Edit:The question Good way to make \textcircled numbers? is related.