81905863 has 4 divisors (see below), whose sum is σ = 88206328. Its totient is φ = 75605400.

The previous prime is 81905851. The next prime is 81905869. The reversal of 81905863 is 36850918.

It is a happy number.

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

It is not a de Polignac number, because 81905863 - 2²⁵ = 48351431 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 (81905869) 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, 3150213 + ... + 3150238.

It is an arithmetic number, because the mean of its divisors is an integer number (22051582).

Almost surely, 2^81905863 is an apocalyptic number.

81905863 is a deficient number, since it is larger than the sum of its proper divisors (6300465).

81905863 is a wasteful number, since it uses less digits than its factorization.

81905863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6300464.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 81905863 is about 9050.1857991977. The cubic root of 81905863 is about 434.2818343261.

The spelling of 81905863 in words is "eighty-one million, nine hundred five thousand, eight hundred sixty-three".