81111840 has 96 divisors (see below), whose sum is σ = 264358080. Its totient is φ = 20880384.

The previous prime is 81111799. The next prime is 81111853. The reversal of 81111840 is 4811118.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 81111840.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11007 + ... + 16833.

It is an arithmetic number, because the mean of its divisors is an integer number (2753730).

Almost surely, 2^81111840 is an apocalyptic number.

81111840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81111840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132179040).

81111840 is an abundant number, since it is smaller than the sum of its proper divisors (183246240).

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

81111840 is a wasteful number, since it uses less digits than its factorization.

81111840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5874 (or 5866 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 24.

The square root of 81111840 is about 9006.2111900621. The cubic root of 81111840 is about 432.8739167842.

Adding to 81111840 its reverse (4811118), we get a palindrome (85922958).

The spelling of 81111840 in words is "eighty-one million, one hundred eleven thousand, eight hundred forty".