81691860084 has 12 divisors (see below), whose sum is σ = 190614340224. Its totient is φ = 27230620024.

The previous prime is 81691860079. The next prime is 81691860221. The reversal of 81691860084 is 48006819618.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3403827492 + ... + 3403827515.

It is an arithmetic number, because the mean of its divisors is an integer number (15884528352).

Almost surely, 2^81691860084 is an apocalyptic number.

It is an amenable number.

81691860084 is an abundant number, since it is smaller than the sum of its proper divisors (108922480140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81691860084 is a wasteful number, since it uses less digits than its factorization.

81691860084 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6807655014 (or 6807655012 counting only the distinct ones).

The product of its (nonzero) digits is 663552, while the sum is 51.

The spelling of 81691860084 in words is "eighty-one billion, six hundred ninety-one million, eight hundred sixty thousand, eighty-four".