81644205516 has 12 divisors (see below), whose sum is σ = 190503146232. Its totient is φ = 27214735168.

The previous prime is 81644205497. The next prime is 81644205521. The reversal of 81644205516 is 61550244618.

It is a tau number, because it is divible by the number of its divisors (12).

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 3 ways as a sum of consecutive naturals, for example, 3401841885 + ... + 3401841908.

It is an arithmetic number, because the mean of its divisors is an integer number (15875262186).

Almost surely, 2^81644205516 is an apocalyptic number.

It is an amenable number.

81644205516 is an abundant number, since it is smaller than the sum of its proper divisors (108858940716).

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

81644205516 is a wasteful number, since it uses less digits than its factorization.

81644205516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6803683800 (or 6803683798 counting only the distinct ones).

The product of its (nonzero) digits is 230400, while the sum is 42.

The spelling of 81644205516 in words is "eighty-one billion, six hundred forty-four million, two hundred five thousand, five hundred sixteen".