129 (number)

129 is the natural number following 128 and preceding 130.

Cardinal	One hundred [and] twenty-nine
Ordinal	129th
Factorization
Roman numeral	CXXIX
Binary	10000001
Hexadecimal	81

This number is the sum of the first ten prime numbers. It is the smallest number that can be expressed as a sum of three squares in four different ways: 11² + 2² + 2² and 10² + 5² + 2² and 8² + 8² + 1² and 8² + 7² + 4².

One hundred twenty-nine is also:

• The designation of a spur route of Interstate 29 in Sioux City, Iowa.
• The year AD 129 or 129 BC.

This page discusses the number 129. For the year, see 129.