81968940 has 72 divisors (see below), whose sum is σ = 253955520. Its totient is φ = 21391104.

The previous prime is 81968903. The next prime is 81968989. The reversal of 81968940 is 4986918.

It is a Harshad number since it is a multiple of its sum of digits (45).

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, 3616 + ... + 13304.

It is an arithmetic number, because the mean of its divisors is an integer number (3527160).

Almost surely, 2^81968940 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 81968940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (126977760).

81968940 is an abundant number, since it is smaller than the sum of its proper divisors (171986580).

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

81968940 is a wasteful number, since it uses less digits than its factorization.

81968940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9751 (or 9746 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 45.

The square root of 81968940 is about 9053.6699741044. The cubic root of 81968940 is about 434.3932881557.

The spelling of 81968940 in words is "eighty-one million, nine hundred sixty-eight thousand, nine hundred forty".