81664471837 has 16 divisors (see below), whose sum is σ = 93165327360. Its totient is φ = 70913532672.

The previous prime is 81664471829. The next prime is 81664471849. The reversal of 81664471837 is 73817446618.

It is a cyclic number.

It is not a de Polignac number, because 81664471837 - 2³ = 81664471829 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81664471877) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 366364 + ... + 545482.

It is an arithmetic number, because the mean of its divisors is an integer number (5822832960).

Almost surely, 2^81664471837 is an apocalyptic number.

It is an amenable number.

81664471837 is a deficient number, since it is larger than the sum of its proper divisors (11500855523).

81664471837 is a wasteful number, since it uses less digits than its factorization.

81664471837 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181212.

The product of its digits is 5419008, while the sum is 55.

The spelling of 81664471837 in words is "eighty-one billion, six hundred sixty-four million, four hundred seventy-one thousand, eight hundred thirty-seven".