81789866305 has 24 divisors (see below), whose sum is σ = 114302461608. Its totient is φ = 56020382208.

The previous prime is 81789866297. The next prime is 81789866309. The reversal of 81789866305 is 50366898718.

It can be written as a sum of positive squares in 4 ways, for example, as 24168744369 + 57621121936 = 155463^2 + 240044^2 .

It is not a de Polignac number, because 81789866305 - 2³ = 81789866297 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81789866309) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 24537 + ... + 405193.

It is an arithmetic number, because the mean of its divisors is an integer number (4762602567).

Almost surely, 2^81789866305 is an apocalyptic number.

It is an amenable number.

81789866305 is a deficient number, since it is larger than the sum of its proper divisors (32512595303).

81789866305 is a wasteful number, since it uses less digits than its factorization.

81789866305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 381553 (or 381546 counting only the distinct ones).

The product of its (nonzero) digits is 17418240, while the sum is 61.

The spelling of 81789866305 in words is "eighty-one billion, seven hundred eighty-nine million, eight hundred sixty-six thousand, three hundred five".