81696438529 has 4 divisors (see below), whose sum is σ = 82505314260. Its totient is φ = 80887562800.

The previous prime is 81696438521. The next prime is 81696438547. The reversal of 81696438529 is 92583469618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 92583469618 = 2 ⋅46291734809.

It can be written as a sum of positive squares in 2 ways, for example, as 68631948529 + 13064490000 = 261977^2 + 114300^2 .

It is a cyclic number.

It is not a de Polignac number, because 81696438529 - 2³ = 81696438521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81696438521) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 404437714 + ... + 404437915.

It is an arithmetic number, because the mean of its divisors is an integer number (20626328565).

Almost surely, 2^81696438529 is an apocalyptic number.

It is an amenable number.

81696438529 is a deficient number, since it is larger than the sum of its proper divisors (808875731).

81696438529 is a wasteful number, since it uses less digits than its factorization.

81696438529 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 808875730.

The product of its digits is 22394880, while the sum is 61.

The spelling of 81696438529 in words is "eighty-one billion, six hundred ninety-six million, four hundred thirty-eight thousand, five hundred twenty-nine".