129 (number)

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

 ← 128 129 130 →
Cardinalone hundred twenty-nine
Ordinal129th
(one hundred twenty-ninth)
Factorization3 × 43
Divisors1, 3, 43, 129
Greek numeralΡΚΘ´
Roman numeralCXXIX
Binary100000012
Ternary112103
Octal2018
DuodecimalA912

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: ${\displaystyle 11^{2}+2^{2}+2^{2}}$ , ${\displaystyle 10^{2}+5^{2}+2^{2}}$ , ${\displaystyle 8^{2}+8^{2}+1^{2}}$ , and ${\displaystyle 8^{2}+7^{2}+4^{2}}$ .

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.[1]

129 is a repdigit in base 6 (333).

129 is a happy number.[2]

In transportation

• LZ 129 Hindenburg was a German zeppelin which went up in flames while landing on May 6, 1937
• London Buses route 129 is a Transport for London contracted bus route in London
• STS-129 was a Space Shuttle mission to the International Space Station, flown in November 2009 by the shuttle Atlantis.

129 is also: