This character is a Other Punctuation and is commonly used, that is, in no specific script.
The glyph is a small version of the glyph Number Sign. Its East Asian Width is wide. In bidirectional text it is written as end of a European number, e.g., a currency symbol, from left to right. When changing direction it is not mirrored. U+FE5F offers a line break opportunity at its position, except in some numeric contexts.
The Wikipedia has the following information about this codepoint:
The symbol # is known variously in English-speaking regions as the number sign, hash, or pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔.
Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as "hashtags", and from that, the symbol itself is sometimes called a hashtag.
The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes.
Representations
System
Representation (click value to copy)
Nº
65119
UTF-8
EF B9 9F
UTF-16
FE 5F
UTF-32
00 00 FE 5F
URL-Quoted
%EF%B9%9F
HTML hex reference
﹟
Wrong windows-1252 Mojibake
﹟
Encoding: BIG5 (hex bytes)
A1 CC
Encoding: BIG5HKSCS (hex bytes)
A1 CC
Encoding: CP950 (hex bytes)
A1 CC
Encoding: GBK (hex bytes)
A9 7C
Encoding: GB18030 (hex bytes)
A9 7C
Adobe Glyph List
numbersignsmall
RFC 5137
\u'FE5F'
Bash and Zsh inside echo -e
\uFE5F
C and C++
\uFE5F
C#
\uFE5F
CSS
\00FE5F
Excel
=UNICHAR(65119)
Go
\uFE5F
JavaScript
\uFE5F
Modern JavaScript since ES6
\u{fe5f}
JSON
\uFE5F
Java
\uFE5F
Lua
\u{FE5F}
Matlab
char(65119)
Perl
"\x{FE5F}"
PHP
\u{fe5f}
PostgreSQL
U&'\FE5F'
PowerShell
`u{FE5F}
Python
\uFE5F
Ruby
\u{fe5f}
Rust
\u{fe5f}
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