81688161680 has 40 divisors (see below), whose sum is σ = 191805440184. Its totient is φ = 32351744000.

The previous prime is 81688161679. The next prime is 81688161697. The reversal of 81688161680 is 8616188618.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 14774888704 + 66913272976 = 121552^2 + 258676^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5046881 + ... + 5063040.

Almost surely, 2^81688161680 is an apocalyptic number.

81688161680 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81688161680 is an abundant number, since it is smaller than the sum of its proper divisors (110117278504).

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

81688161680 is a wasteful number, since it uses less digits than its factorization.

81688161680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10110035 (or 10110029 counting only the distinct ones).

The product of its (nonzero) digits is 884736, while the sum is 53.

The spelling of 81688161680 in words is "eighty-one billion, six hundred eighty-eight million, one hundred sixty-one thousand, six hundred eighty".