81538317844 has 12 divisors (see below), whose sum is σ = 142694315764. Its totient is φ = 40768513344.

The previous prime is 81538317841. The next prime is 81538317853. The reversal of 81538317844 is 44871383518.

It can be written as a sum of positive squares in 2 ways, for example, as 32458346244 + 49079971600 = 180162^2 + 221540^2 .

It is a hoax number, since the sum of its digits (52) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 81538317791 and 81538317800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81538317841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 226222 + ... + 462874.

Almost surely, 2^81538317844 is an apocalyptic number.

It is an amenable number.

81538317844 is a deficient number, since it is larger than the sum of its proper divisors (61155997920).

81538317844 is a wasteful number, since it uses less digits than its factorization.

81538317844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322794 (or 322792 counting only the distinct ones).

The product of its digits is 2580480, while the sum is 52.

The spelling of 81538317844 in words is "eighty-one billion, five hundred thirty-eight million, three hundred seventeen thousand, eight hundred forty-four".