81993739896 has 24 divisors (see below), whose sum is σ = 222066379080. Its totient is φ = 27331246608.

The previous prime is 81993739871. The next prime is 81993739909. The reversal of 81993739896 is 69893739918.

It is a happy number.

81993739896 is a `hidden beast` number, since 81 + 9 + 9 + 373 + 98 + 96 = 666.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (72), and also a Moran number because the ratio is a prime number: 1138801943 = 81993739896 / (8 + 1 + 9 + 9 + 3 + 7 + 3 + 9 + 8 + 9 + 6).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 569400900 + ... + 569401043.

It is an arithmetic number, because the mean of its divisors is an integer number (9252765795).

Almost surely, 2^81993739896 is an apocalyptic number.

It is an amenable number.

81993739896 is an abundant number, since it is smaller than the sum of its proper divisors (140072639184).

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

81993739896 is a wasteful number, since it uses less digits than its factorization.

81993739896 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1138801955 (or 1138801948 counting only the distinct ones).

The product of its digits is 158723712, while the sum is 72.

The spelling of 81993739896 in words is "eighty-one billion, nine hundred ninety-three million, seven hundred thirty-nine thousand, eight hundred ninety-six".