81968640 has 160 divisors (see below), whose sum is σ = 282544416. Its totient is φ = 20152320.

The previous prime is 81968639. The next prime is 81968651. The reversal of 81968640 is 4686918.

It is a tau number, because it is divible by the number of its divisors (160).

It is a junction number, because it is equal to n+sod(n) for n = 81968592 and 81968601.

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 15 ways as a sum of consecutive naturals, for example, 99430 + ... + 100250.

Almost surely, 2^81968640 is an apocalyptic number.

81968640 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 81968640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (141272208).

81968640 is an abundant number, since it is smaller than the sum of its proper divisors (200575776).

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

81968640 is a wasteful number, since it uses less digits than its factorization.

81968640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 860 (or 844 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 42.

The square root of 81968640 is about 9053.6534062223. The cubic root of 81968640 is about 434.3927582064.

It can be divided in two parts, 8196 and 8640, that added together give a triangular number (16836 = T₁₈₃).

The spelling of 81968640 in words is "eighty-one million, nine hundred sixty-eight thousand, six hundred forty".