81291 has 16 divisors (see below), whose sum is σ = 128000. Its totient is φ = 45864.

The previous prime is 81283. The next prime is 81293. The reversal of 81291 is 19218.

It is not a de Polignac number, because 81291 - 2³ = 81283 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81293) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 990 + ... + 1068.

It is an arithmetic number, because the mean of its divisors is an integer number (8000).

2⁸¹²⁹¹ is an apocalyptic number.

81291 is a deficient number, since it is larger than the sum of its proper divisors (46709).

81291 is an equidigital number, since it uses as much as digits as its factorization.

81291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103 (or 89 counting only the distinct ones).

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

The square root of 81291 is about 285.1157659618. The cubic root of 81291 is about 43.3192393350.

It can be divided in two parts, 812 and 91, that added together give a triangular number (903 = T₄₂).

The spelling of 81291 in words is "eighty-one thousand, two hundred ninety-one".