81684708085 has 4 divisors (see below), whose sum is σ = 98021649708. Its totient is φ = 65347766464.

The previous prime is 81684708037. The next prime is 81684708143. The reversal of 81684708085 is 58080748618.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 33882133041 + 47802575044 = 184071^2 + 218638^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81684708085 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 3 ways as a sum of consecutive naturals, for example, 8168470804 + ... + 8168470813.

It is an arithmetic number, because the mean of its divisors is an integer number (24505412427).

Almost surely, 2^81684708085 is an apocalyptic number.

It is an amenable number.

81684708085 is a deficient number, since it is larger than the sum of its proper divisors (16336941623).

81684708085 is a wasteful number, since it uses less digits than its factorization.

81684708085 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16336941622.

The product of its (nonzero) digits is 3440640, while the sum is 55.

The spelling of 81684708085 in words is "eighty-one billion, six hundred eighty-four million, seven hundred eight thousand, eighty-five".