81691860085 has 16 divisors (see below), whose sum is σ = 106994976192. Its totient is φ = 59382870400.

The previous prime is 81691860079. The next prime is 81691860221. The reversal of 81691860085 is 58006819618.

It is not a de Polignac number, because 81691860085 - 2⁷ = 81691859957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 254896 + ... + 477865.

It is an arithmetic number, because the mean of its divisors is an integer number (6687186012).

Almost surely, 2^81691860085 is an apocalyptic number.

It is an amenable number.

81691860085 is a deficient number, since it is larger than the sum of its proper divisors (25303116107).

81691860085 is a wasteful number, since it uses less digits than its factorization.

81691860085 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 734804.

The product of its (nonzero) digits is 829440, while the sum is 52.

The spelling of 81691860085 in words is "eighty-one billion, six hundred ninety-one million, eight hundred sixty thousand, eighty-five".