Pentadecimal

Numeral systems by culture
Hindu-Arabic numerals
Western Arabic (Hindu numerals) Eastern Arabic Indian family Tamil	Burmese Khmer Lao Mongolian Thai
East Asian numerals
Chinese Japanese Suzhou	Korean Vietnamese Counting rods
Alphabetic numerals
Abjad Armenian Āryabhaṭa Cyrillic	Ge'ez Greek Georgian Hebrew
other historical systems
Aegean Attic Babylonian Brahmi Egyptian Etruscan Inuit	Kharosthi Mayan Quipu Roman
Positional systems by base
Decimal (10)
2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 20, 24, 30, 36, 60, 64
Balanced ternary
Non-positional system
Unary numeral system (Base 1)
List of numeral systems

The pentadecimal (base-15) positional notation system is based on the number fifteen. Comparatively, the decimal system is based on the number ten, the hexadecimal system is based on the number sixteen, and so on. Another name used for the base-15 system is quindecimal (although this term can be confused with quinary which is a base-5 notation system).

Pentadecimal requires fifteen symbols. Since there are only ten common decimal digits, the notation can be extended by using letters A, B, C, D and E to represent values 10, 11, 12, 13 and 14, respectively. For example, decimal values 0 to 20 in pentadecimal would be: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, 10, 11, 12, 13, 14, 15. The pentadecimal number 373 would be 783 in decimal.

This numeric base is infrequently used. It finds applications in mathematics as well as fields such as telephony routing over IP (see RFC 3219) and other specialized uses.

Natural languages

The Huli language of Papua New Guinea is reported to have base-15 numerals. Ngui means 15, ngui ki means 15×2 = 30, and ngui ngui means 15×15 = 225.