81040 has 20 divisors (see below), whose sum is σ = 188604. Its totient is φ = 32384.

The previous prime is 81031. The next prime is 81041. The reversal of 81040 is 4018.

It can be written as a sum of positive squares in 2 ways, for example, as 9216 + 71824 = 96^2 + 268^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a self number, because there is not a number n which added to its sum of digits gives 81040.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 427 + ... + 586.

2⁸¹⁰⁴⁰ is an apocalyptic number.

81040 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81040 is an abundant number, since it is smaller than the sum of its proper divisors (107564).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (94302).

81040 is a wasteful number, since it uses less digits than its factorization.

81040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1026 (or 1020 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 81040 is about 284.6752535785. The cubic root of 81040 is about 43.2746081573.

Adding to 81040 its reverse (4018), we get a palindrome (85058).

It can be divided in two parts, 810 and 40, that multiplied together give a square (32400 = 180²).

The spelling of 81040 in words is "eighty-one thousand, forty".