129861 has 12 divisors (see below), whose sum is σ = 192192. Its totient is φ = 84456.

The previous prime is 129853. The next prime is 129887. The reversal of 129861 is 168921.

It is not a de Polignac number, because 129861 - 2³ = 129853 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 270 + ... + 576.

It is an arithmetic number, because the mean of its divisors is an integer number (16016).

2¹²⁹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

129861 is a deficient number, since it is larger than the sum of its proper divisors (62331).

129861 is a wasteful number, since it uses less digits than its factorization.

129861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360 (or 357 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 129861 is about 360.3623176749. The cubic root of 129861 is about 50.6399087320.

Subtracting 129861 from its reverse (168921), we obtain a triangular number (39060 = T₂₇₉).

It can be divided in two parts, 129 and 861, that added together give a triangular number (990 = T₄₄).

The spelling of 129861 in words is "one hundred twenty-nine thousand, eight hundred sixty-one".