81240 has 32 divisors (see below), whose sum is σ = 244080. Its totient is φ = 21632.

The previous prime is 81239. The next prime is 81281. The reversal of 81240 is 4218.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 219 + ... + 458.

2⁸¹²⁴⁰ is an apocalyptic number.

It is an amenable number.

81240 is an abundant number, since it is smaller than the sum of its proper divisors (162840).

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 (122040).

81240 is a wasteful number, since it uses less digits than its factorization.

81240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 691 (or 687 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 81240 is about 285.0263145746. The cubic root of 81240 is about 43.3101782934.

Subtracting from 81240 its sum of digits (15), we obtain a square (81225 = 285²).

Adding to 81240 its reverse (4218), we get a palindrome (85458).

The spelling of 81240 in words is "eighty-one thousand, two hundred forty".