In Spanish the the accepted abbreviations, according to Real Academia Española, are:
n.º
nro.
núm
#
(see http://lema.rae.es/dpd/apendices/apendice2.html and http://lema.rae.es/dpd/apendices/apendice4.html)

Although, Nº and No. are widely used.

On Thu, Jul 30, 2015 at 10:38 AM, J Andrew Lipscomb <silverpie2@mac.com> wrote:
Le 29 juil. 2015 à 13:24, Paul Eggert <eggert@cs.ucla.edu> a écrit :
>
> Gwillim Law wrote:
>> I don't see any solecism. The superscript o is not an ordinal indicator
>> here. Nº is not a synonym for Nth. The words that are abbreviated Nº are
>> masculine nouns: French numéro, Spanish número, Italian numero, etc.
>
> Perhaps I'm being pedantic, but I think º (U+00BA MASCULINE ORDINAL INDICATOR) should be used only with

In French at least, the second character of N° is properly U+00B0 DEGREE SIGN.