81563720772 has 12 divisors (see below), whose sum is σ = 190315348496. Its totient is φ = 27187906920.

The previous prime is 81563720761. The next prime is 81563720779. The reversal of 81563720772 is 27702736518.

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

It is not an unprimeable number, because it can be changed into a prime (81563720779) by changing a digit.

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, 3398488354 + ... + 3398488377.

Almost surely, 2^81563720772 is an apocalyptic number.

It is an amenable number.

81563720772 is an abundant number, since it is smaller than the sum of its proper divisors (108751627724).

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

81563720772 is a wasteful number, since it uses less digits than its factorization.

81563720772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6796976738 (or 6796976736 counting only the distinct ones).

The product of its (nonzero) digits is 987840, while the sum is 48.

The spelling of 81563720772 in words is "eighty-one billion, five hundred sixty-three million, seven hundred twenty thousand, seven hundred seventy-two".