81912823 has 4 divisors (see below), whose sum is σ = 81942280. Its totient is φ = 81883368.

The previous prime is 81912811. The next prime is 81912847. The reversal of 81912823 is 32821918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 32821918 = 2 ⋅16410959.

It is a cyclic number.

It is not a de Polignac number, because 81912823 - 2²⁵ = 48358391 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 (81972823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10065 + ... + 16282.

It is an arithmetic number, because the mean of its divisors is an integer number (20485570).

Almost surely, 2^81912823 is an apocalyptic number.

81912823 is a deficient number, since it is larger than the sum of its proper divisors (29457).

81912823 is a wasteful number, since it uses less digits than its factorization.

81912823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29456.

The product of its digits is 6912, while the sum is 34.

The square root of 81912823 is about 9050.5703135217. The cubic root of 81912823 is about 434.2941350978.

The spelling of 81912823 in words is "eighty-one million, nine hundred twelve thousand, eight hundred twenty-three".