129 (number)

129 (one hundred [and] twenty-nine) is the natural number following 128 and preceding 130.

In mathematics

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: $11^2+2^2+2^2$, $10^2+5^2+2^2$, $8^2+8^2+1^2$, and $8^2+7^2+4^2$.

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.

129 is a repdigit in base 6 (333).

129 is a happy number.

129 is a centered octahedral number.