81539987616 has 72 divisors (see below), whose sum is σ = 232049350260. Its totient is φ = 27160068096.

The previous prime is 81539987597. The next prime is 81539987621. The reversal of 81539987616 is 61678993518.

81539987616 is a `hidden beast` number, since 8 + 1 + 5 + 3 + 9 + 9 + 8 + 7 + 616 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 58949897616 + 22590090000 = 242796^2 + 150300^2 .

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 (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 292320 + ... + 498528.

Almost surely, 2^81539987616 is an apocalyptic number.

It is an amenable number.

81539987616 is an abundant number, since it is smaller than the sum of its proper divisors (150509362644).

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

81539987616 is a wasteful number, since it uses less digits than its factorization.

81539987616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207598 (or 207587 counting only the distinct ones).

The product of its digits is 19595520, while the sum is 63.

The spelling of 81539987616 in words is "eighty-one billion, five hundred thirty-nine million, nine hundred eighty-seven thousand, six hundred sixteen".