This character is a Other Symbol and is commonly used, that is, in no specific script.
The glyph is a square composition of the glyphs Glyph for U+006ELatin Small Letter N, Glyph for U+006DLatin Small Letter M. Its East Asian Width is wide. In bidirectional text it is written from left to right. When changing direction it is not mirrored. U+339A offers a line break opportunity at its position, except in some numeric contexts.
The Wikipedia has the following information about this codepoint:
The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling), is a unit of length in the International System of Units (SI), equal to one billionth (short scale) of a meter (0.000000001 m) and to 1000 picometres. One nanometre can be expressed in scientific notation as 1 × 10-9 m and as 1/1000000000 m.
Representations
System
Representation (click value to copy)
Nº
13210
UTF-8
E3 8E 9A
UTF-16
33 9A
UTF-32
00 00 33 9A
URL-Quoted
%E3%8E%9A
HTML hex reference
㎚
Wrong windows-1252 Mojibake
㎚
Encoding: CP949 (hex bytes)
A7 AC
Encoding: EUC_KR (hex bytes)
A7 AC
Encoding: GB18030 (hex bytes)
81 39 E5 36
Encoding: ISO2022_JP_2 (hex bytes)
1B 24 28 43 27 2C 1B 28 42
Encoding: ISO2022_KR (hex bytes)
1B 24 29 43 0E 27 2C 0F
Encoding: JOHAB (hex bytes)
DC 3C
Adobe Glyph List
nmsquare
RFC 5137
\u'339A'
Bash and Zsh inside echo -e
\u339A
C and C++
\u339A
C#
\u339A
CSS
\00339A
Excel
=UNICHAR(13210)
Go
\u339A
JavaScript
\u339A
Modern JavaScript since ES6
\u{339a}
JSON
\u339A
Java
\u339A
Lua
\u{339A}
Matlab
char(13210)
Perl
"\x{339A}"
PHP
\u{339a}
PostgreSQL
U&'\339A'
PowerShell
`u{339A}
Python
\u339A
Ruby
\u{339a}
Rust
\u{339a}
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