81390594265 has 4 divisors (see below), whose sum is σ = 97668713124. Its totient is φ = 65112475408.

The previous prime is 81390594169. The next prime is 81390594269. The reversal of 81390594265 is 56249509318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56249509318 = 2 ⋅28124754659.

It can be written as a sum of positive squares in 2 ways, for example, as 44932128784 + 36458465481 = 211972^2 + 190941^2 .

It is a cyclic number.

It is not a de Polignac number, because 81390594265 - 2²⁵ = 81357039833 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81390594269) 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, 8139059422 + ... + 8139059431.

It is an arithmetic number, because the mean of its divisors is an integer number (24417178281).

Almost surely, 2^81390594265 is an apocalyptic number.

It is an amenable number.

81390594265 is a deficient number, since it is larger than the sum of its proper divisors (16278118859).

81390594265 is a wasteful number, since it uses less digits than its factorization.

81390594265 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16278118858.

The product of its (nonzero) digits is 2332800, while the sum is 52.

The spelling of 81390594265 in words is "eighty-one billion, three hundred ninety million, five hundred ninety-four thousand, two hundred sixty-five".