Mathematical Monospace Digit Nine
HTML Entity Browser Test:

U+1D7FF is the Unicode hex value of the character Mathematical Monospace Digit Nine, which is categorized as "decimal digit number" in the Unicode 6.0 character table.

In addition, U+1D7FF is a composite character comprising of one or more other Unicode characters modified or combined.

Unicode Character Information
Unicode Hex U+1D7FF
General Category Decimal Digit Number [Code: Nd]
Canonical Combining Class 0
Bidirectional Category EN
Decomposition Mapping <font> 0039
Numeric Value 9
Mirrored N
Unicode Character Encodings
Mathematical Monospace Digit Nine HTML Entity &#120831; (decimal entity), &#x1D7FF; (hex entity)
Windows Key Code Alt 120831 or Alt +1D7FF1
Programming Source Code Encodings Python hex: u"\u1D7FF", Hex for C++ and Java: "\u1D7FF"
UTF-8 Hexadecimal Encoding 0xF09D9FBF
1 To type a Unicode symbol in Windows, hold down the ALT key and enter the decimal or hexadecimal code provided using the numeric keypad. The decimal alt code (Alt 120831) will only work on computers with support for this Unicode character in the active code page. The hexadecimal alt code (Alt +1D7FF) will work for all Unicode characters provided Hex input from the numeric keypad is enabled.
* If the Mathematical Monospace Digit Nine character does not display correctly in your browser, you may not have a Unicode font on your system that supports this particular symbol.