81091928 has 16 divisors (see below), whose sum is σ = 158658480. Its totient is φ = 38783008.

The previous prime is 81091919. The next prime is 81091949. The reversal of 81091928 is 82919018.

It is a junction number, because it is equal to n+sod(n) for n = 81091891 and 81091900.

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, 220175 + ... + 220542.

It is an arithmetic number, because the mean of its divisors is an integer number (9916155).

Almost surely, 2^81091928 is an apocalyptic number.

It is an amenable number.

81091928 is a deficient number, since it is larger than the sum of its proper divisors (77566552).

81091928 is a wasteful number, since it uses less digits than its factorization.

81091928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 440746 (or 440742 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 81091928 is about 9005.1056629004. The cubic root of 81091928 is about 432.8384920716.

The spelling of 81091928 in words is "eighty-one million, ninety-one thousand, nine hundred twenty-eight".