81405 has 24 divisors (see below), whose sum is σ = 148512. Its totient is φ = 42768.

The previous prime is 81401. The next prime is 81409. The reversal of 81405 is 50418.

It is an interprime number because it is at equal distance from previous prime (81401) and next prime (81409).

It is not a de Polignac number, because 81405 - 2² = 81401 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 81405.

It is not an unprimeable number, because it can be changed into a prime (81401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1182 + ... + 1248.

It is an arithmetic number, because the mean of its divisors is an integer number (6188).

2⁸¹⁴⁰⁵ is an apocalyptic number.

It is an amenable number.

81405 is a deficient number, since it is larger than the sum of its proper divisors (67107).

81405 is an equidigital number, since it uses as much as digits as its factorization.

81405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87 (or 75 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 81405 is about 285.3156147147. The cubic root of 81405 is about 43.3394797330.

The spelling of 81405 in words is "eighty-one thousand, four hundred five".