81729 has 10 divisors (see below), whose sum is σ = 122210. Its totient is φ = 54432.

The previous prime is 81727. The next prime is 81737. The reversal of 81729 is 92718.

It can be written as a sum of positive squares in only one way, i.e., 63504 + 18225 = 252^2 + 135^2 .

It is not a de Polignac number, because 81729 - 2¹ = 81727 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

81729 is a modest number, since divided by 729 gives 81 as remainder.

It is not an unprimeable number, because it can be changed into a prime (81727) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 424 + ... + 585.

It is an arithmetic number, because the mean of its divisors is an integer number (12221).

2⁸¹⁷²⁹ is an apocalyptic number.

It is an amenable number.

81729 is a deficient number, since it is larger than the sum of its proper divisors (40481).

81729 is a wasteful number, since it uses less digits than its factorization.

81729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1021 (or 1012 counting only the distinct ones).

The product of its digits is 1008, while the sum is 27.

The square root of 81729 is about 285.8828431368. The cubic root of 81729 is about 43.3969020986.

It can be divided in two parts, 81 and 729, that multiplied together give a 10-th power (59049 = 3¹⁰).

The spelling of 81729 in words is "eighty-one thousand, seven hundred twenty-nine".