129 (number)
129 (one hundred [and] twenty-nine) is the natural number following 128 and preceding 130.
In mathematicsEdit
129 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: <math>11^2+2^2+2^2</math>, <math>10^2+5^2+2^2</math>, <math>8^2+8^2+1^2</math>, and <math>8^2+7^2+4^2</math>.
129 is the product of only two primes, 3 and 43, making 129 a semiprime. Since 3 and 43 are both Gaussian primes, this means that 129 is a Blum integer.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
129 is a repdigit in base 6 (333).
129 is a happy number.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
129 is a centered octahedral number.<ref>Template:Cite OEIS</ref>