81928939 has 4 divisors (see below), whose sum is σ = 84571840. Its totient is φ = 79286040.

The previous prime is 81928927. The next prime is 81928949. The reversal of 81928939 is 93982918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 93982918 = 2 ⋅46991459.

It is a cyclic number.

It is not a de Polignac number, because 81928939 - 2⁷ = 81928811 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81928892 and 81928901.

It is not an unprimeable number, because it can be changed into a prime (81928919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1321404 + ... + 1321465.

It is an arithmetic number, because the mean of its divisors is an integer number (21142960).

Almost surely, 2^81928939 is an apocalyptic number.

81928939 is a deficient number, since it is larger than the sum of its proper divisors (2642901).

81928939 is a wasteful number, since it uses less digits than its factorization.

81928939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2642900.

The product of its digits is 279936, while the sum is 49.

The square root of 81928939 is about 9051.4606003672. The cubic root of 81928939 is about 434.3226150722.

The spelling of 81928939 in words is "eighty-one million, nine hundred twenty-eight thousand, nine hundred thirty-nine".