81568440 has 96 divisors (see below), whose sum is σ = 273686400. Its totient is φ = 21047040.

The previous prime is 81568433. The next prime is 81568447. The reversal of 81568440 is 4486518.

It is an interprime number because it is at equal distance from previous prime (81568433) and next prime (81568447).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81568395 and 81568404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81568447) 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, 7506 + ... + 14814.

It is an arithmetic number, because the mean of its divisors is an integer number (2850900).

Almost surely, 2^81568440 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81568440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (136843200).

81568440 is an abundant number, since it is smaller than the sum of its proper divisors (192117960).

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

81568440 is a wasteful number, since it uses less digits than its factorization.

81568440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7357 (or 7350 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The square root of 81568440 is about 9031.5247882071. The cubic root of 81568440 is about 433.6846513238.

The spelling of 81568440 in words is "eighty-one million, five hundred sixty-eight thousand, four hundred forty".