81915844 has 6 divisors (see below), whose sum is σ = 143352734. Its totient is φ = 40957920.

The previous prime is 81915833. The next prime is 81915871. The reversal of 81915844 is 44851918.

It can be written as a sum of positive squares in only one way, i.e., 81685444 + 230400 = 9038^2 + 480^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81915797 and 81915806.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10239477 + ... + 10239484.

Almost surely, 2^81915844 is an apocalyptic number.

It is an amenable number.

81915844 is a deficient number, since it is larger than the sum of its proper divisors (61436890).

81915844 is a wasteful number, since it uses less digits than its factorization.

81915844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20478965 (or 20478963 counting only the distinct ones).

The product of its digits is 46080, while the sum is 40.

The square root of 81915844 is about 9050.7372075428. The cubic root of 81915844 is about 434.2994740521.

The spelling of 81915844 in words is "eighty-one million, nine hundred fifteen thousand, eight hundred forty-four".