The LaTeX command for registered (®) is \textregistered.
\textregisteredWriting a paper? The table generator and the BibTeX cleaner are one click away, no account.
Write \textregistered in normal text, outside math mode. It is part of core LaTeX, so no extra package is required.
\textregistered is a text command: inside a formula it needs \text{...} from amsmath. With XeLaTeX or LuaLaTeX you can also type ® directly.
Open this example in the live preview: it renders as you type, with no compiler and no signup.
\textasciicircum\textbackslash\textasteriskcentered\slash``''\textcopyright\texttrademark\pounds\texteuro\textyen\dag\ddag\SText symbols in LaTeX: the full table or search all 350+ LaTeX symbols.
Use \textregistered in normal text; it needs no extra package. For example, \textregistered.
None: \textregistered is built into LaTeX, so no extra package is required.