81975816 has 72 divisors (see below), whose sum is σ = 240445530. Its totient is φ = 25219584.

The previous prime is 81975809. The next prime is 81975869. The reversal of 81975816 is 61857918.

It can be written as a sum of positive squares in 3 ways, for example, as 41602500 + 40373316 = 6450^2 + 6354^2 .

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

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 17 ways as a sum of consecutive naturals, for example, 8800 + ... + 15536.

Almost surely, 2^81975816 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 81975816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (120222765).

81975816 is an abundant number, since it is smaller than the sum of its proper divisors (158469714).

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

81975816 is a wasteful number, since it uses less digits than its factorization.

81975816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6775 (or 6755 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 81975816 is about 9054.0497016528. The cubic root of 81975816 is about 434.4054342391.

The spelling of 81975816 in words is "eighty-one million, nine hundred seventy-five thousand, eight hundred sixteen".