Enclosed R or circled Latin R (Ⓡ or ⓡ) is a typographical symbol. As one of many enclosed alphanumerics, the symbol is an "R" within a circle. Its most notable usage is as the registered trademark symbol (®), however, that has a different unicode because some fonts place the RTM symbol in superscript by default, but not enclosed R.
Encodings
The symbols can be generated with the unicode definitions U+24C7 Ⓡ Circled Latin capital letter R (HTML Ⓡ) and U+24E1 ⓡ CIRCLED LATIN SMALL LETTER R (HTML ⓡ)
References
Enclosed R Wikipedia(Text) CC BY-SA