81907923 has 4 divisors (see below), whose sum is σ = 109210568. Its totient is φ = 54605280.

The previous prime is 81907913. The next prime is 81907951. The reversal of 81907923 is 32970918.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 81907923 - 2¹⁰ = 81906899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81907913) 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, 13651318 + ... + 13651323.

It is an arithmetic number, because the mean of its divisors is an integer number (27302642).

Almost surely, 2^81907923 is an apocalyptic number.

81907923 is a deficient number, since it is larger than the sum of its proper divisors (27302645).

81907923 is a wasteful number, since it uses less digits than its factorization.

81907923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27302644.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 81907923 is about 9050.2996083003. The cubic root of 81907923 is about 434.2854751443.

The spelling of 81907923 in words is "eighty-one million, nine hundred seven thousand, nine hundred twenty-three".