81215712 has 72 divisors (see below), whose sum is σ = 234181584. Its totient is φ = 26694144.

The previous prime is 81215707. The next prime is 81215723. The reversal of 81215712 is 21751218.

It is a tau number, because it is divible by the number of its divisors (72).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19093 + ... + 22955.

It is an arithmetic number, because the mean of its divisors is an integer number (3252522).

Almost surely, 2^81215712 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 81215712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117090792).

81215712 is an abundant number, since it is smaller than the sum of its proper divisors (152965872).

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

81215712 is a wasteful number, since it uses less digits than its factorization.

81215712 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3952 (or 3941 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 81215712 is about 9011.9760319255. The cubic root of 81215712 is about 433.0586177258.

The spelling of 81215712 in words is "eighty-one million, two hundred fifteen thousand, seven hundred twelve".