81129 has 4 divisors (see below), whose sum is σ = 108176. Its totient is φ = 54084.

The previous prime is 81119. The next prime is 81131. The reversal of 81129 is 92118.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81129 - 2⁵ = 81097 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81119) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13519 + ... + 13524.

It is an arithmetic number, because the mean of its divisors is an integer number (27044).

2⁸¹¹²⁹ is an apocalyptic number.

It is an amenable number.

81129 is a deficient number, since it is larger than the sum of its proper divisors (27047).

81129 is a wasteful number, since it uses less digits than its factorization.

81129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27046.

The product of its digits is 144, while the sum is 21.

The square root of 81129 is about 284.8315291536. The cubic root of 81129 is about 43.2904440863.

It can be divided in two parts, 81 and 129, that added together give a triangular number (210 = T₂₀).

The spelling of 81129 in words is "eighty-one thousand, one hundred twenty-nine".