EDIT Superscript latin small letter o. Is used for example in french for abbrevation of Numéro = Nº.

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EDIT The Numero has a code point of its own: U+2116
In general, the ordinal indicators ª U+00AA (feminine) and º U+00BA (masculine) are used in Italian, Portuguese, and Spanish for writing ordinal numbers. Additionally, Spanish uses them for some abbreviations.

 83.236.181.13