81360864 has 144 divisors (see below), whose sum is σ = 257572224. Its totient is φ = 24192000.

The previous prime is 81360841. The next prime is 81360889. The reversal of 81360864 is 46806318.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (144).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 115714 + ... + 116414.

It is an arithmetic number, because the mean of its divisors is an integer number (1788696).

Almost surely, 2^81360864 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 81360864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128786112).

81360864 is an abundant number, since it is smaller than the sum of its proper divisors (176211360).

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

81360864 is a wasteful number, since it uses less digits than its factorization.

81360864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 761 (or 750 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 81360864 is about 9020.0257205842. The cubic root of 81360864 is about 433.3164574624.

The spelling of 81360864 in words is "eighty-one million, three hundred sixty thousand, eight hundred sixty-four".