81904123 has 4 divisors (see below), whose sum is σ = 93604720. Its totient is φ = 70203528.

The previous prime is 81904099. The next prime is 81904153. The reversal of 81904123 is 32140918.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 32140918 = 2 ⋅16070459.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81904123 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81904091 and 81904100.

It is not an unprimeable number, because it can be changed into a prime (81904153) 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, 5850288 + ... + 5850301.

It is an arithmetic number, because the mean of its divisors is an integer number (23401180).

Almost surely, 2^81904123 is an apocalyptic number.

81904123 is a deficient number, since it is larger than the sum of its proper divisors (11700597).

81904123 is a wasteful number, since it uses less digits than its factorization.

81904123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11700596.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 81904123 is about 9050.0896680641. The cubic root of 81904123 is about 434.2787590243.

The spelling of 81904123 in words is "eighty-one million, nine hundred four thousand, one hundred twenty-three".