# How can I write upside down real numbers symbol ($\mathbb{R}$)?

1. \umathbb{R} for u​pside down
2. \rmathbb{R} for r​eflected
3. \fmathbb{R} for f​lipped
\documentclass{article}

\usepackage{amsfonts}
\usepackage{graphicx}

\makeatletter
\newcommand{\umathbb}[1]{{\mathpalette$email protected]{#1}}} \newcommand{\[email protected]}[2]{% \raisebox{\depth}{\rotatebox{180}{\[email protected]#1\mathbb{#2}}}% } \newcommand{\rmathbb}[1]{{\mathpalette\[email protected]{#1}}} \newcommand{\[email protected]}[2]{% \scalebox{-1}[1]{\[email protected]#1\mathbb{#2}}% } \newcommand{\fmathbb}[1]{{\mathpalette\[email protected]{#1}}} \newcommand{\[email protected]}[2]{% \raisebox{\depth}{\scalebox{1}[-1]{\[email protected]#1\mathbb{#2}}}% } \makeatother \begin{document} A\umathbb{R}B A\rmathbb{R}B A\fmathbb{R}B X_{\umathbb{R}} X_{\rmathbb{R}} X_{\fmathbb{R}} \end{document}  To rotate upside down: \documentclass{article} \usepackage{amsfonts} \usepackage{graphicx} \begin{document} X\rotatebox[origin=c]{180}{\mathbb{R}}X \end{document}  Supports smaller math styles. \documentclass{article} \usepackage{amsfonts,scalerel,graphicx} \newcommand\umathbb[1]{% \ThisStyle{\rotatebox[origin=c]{180}{\SavedStyle\mathbb{#1}}}} \newcommand\rmathbb[1]{% \ThisStyle{\scalebox{-1}[1]{\SavedStyle\mathbb{#1}}}} \newcommand\fmathbb[1]{% \ThisStyle{\scalebox{-1}[1]{\rotatebox[origin=c]{180}{\SavedStyle\mathbb{#1}}}}} \begin{document} \[ A\mathbb{R}B\quad A\umathbb{R}B\quad A\rmathbb{R}B\quad A\fmathbb{R}B$
$X_{\mathbb{R}} X_{\umathbb{R}} X_{\rmathbb{R}} X_{\fmathbb{R}}$
$\mathbb{R}_{\mathbb{R}_{\mathbb{R}}}\quad \umathbb{R}_{\umathbb{R}_{\umathbb{R}}}\quad \rmathbb{R}_{\rmathbb{R}_{\rmathbb{R}}}\quad \fmathbb{R}_{\fmathbb{R}_{\fmathbb{R}}}$
\end{document}