81031920672 has 24 divisors (see below), whose sum is σ = 212708792016. Its totient is φ = 27010640192.

The previous prime is 81031920643. The next prime is 81031920719. The reversal of 81031920672 is 27602913018.

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

It is a self number, because there is not a number n which added to its sum of digits gives 81031920672.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 422041158 + ... + 422041349.

It is an arithmetic number, because the mean of its divisors is an integer number (8862866334).

Almost surely, 2^81031920672 is an apocalyptic number.

It is an amenable number.

81031920672 is an abundant number, since it is smaller than the sum of its proper divisors (131676871344).

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

81031920672 is a wasteful number, since it uses less digits than its factorization.

81031920672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 844082520 (or 844082512 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 39.

The spelling of 81031920672 in words is "eighty-one billion, thirty-one million, nine hundred twenty thousand, six hundred seventy-two".