### Properties of the number 129:

129 = 3 × 43 is semiprime and squarefree.129 has 2 distinct prime factors, 4 divisors, 5 antidivisors and 84 totatives.

129 has an oblong digit sum 12 in base 10.

Reversing the decimal digits of 129 results in an emirpimes.

129 = 1

^{3}+ 4

^{3}+ 4

^{3}is the sum of 3 positive cubes in 1 way.

129 = 65

^{2}- 64

^{2}= 23

^{2}- 20

^{2}is the difference of 2 nonnegative squares in 2 ways.

129 is the difference of 2 positive pentagonal numbers in 1 way.

129 = 2

^{2}+ 5

^{2}+ 10

^{2}is the sum of 3 positive squares.

129

^{2}is the sum of 3 positive squares.

129 is a proper divisor of 173

^{2}- 1.

129 is an emirpimes in (at least) the following bases: 3, 5, 7, 9, 10, 12, 14, 15, 17, 19, 21, 23, 24, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 45, 51, 55, 60, 69, 71, 72, 78, 80, 84, 89, 91, 93, 94, 98, and 100.

129 is palindromic in (at least) the following bases: 2, 6, 42, -7, -16, -32, and -64.

129 in base 6 = 333 and consists of only the digit '3'.

### The number 129 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.A000051: a(n) = 2^n + 1.

A000930: Narayana's cows sequence: a(0) = a(1) = a(2) = 1; thereafter a(n) = a(n-1) + a(n-3).

A000959: Lucky numbers.

A001358: Semiprimes (or biprimes): products of two primes.

A001969: Evil numbers: numbers with an even number of 1's in their binary expansion.

A005408: The odd numbers: a(n) = 2*n + 1.

A006881: Squarefree semiprimes: Numbers that are the product of two distinct primes.

A007504: Sum of first n primes.

A008585: a(n) = 3*n.

A016813: a(n) = 4n + 1.