81806439 has 32 divisors (see below), whose sum is σ = 131298048. Its totient is φ = 44640000.

The previous prime is 81806393. The next prime is 81806447. The reversal of 81806439 is 93460818.

It is not a de Polignac number, because 81806439 - 2⁸ = 81806183 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a junction number, because it is equal to n+sod(n) for n = 81806397 and 81806406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81806539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15264 + ... + 19914.

It is an arithmetic number, because the mean of its divisors is an integer number (4103064).

Almost surely, 2^81806439 is an apocalyptic number.

81806439 is a deficient number, since it is larger than the sum of its proper divisors (49491609).

81806439 is a wasteful number, since it uses less digits than its factorization.

81806439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4719.

The product of its (nonzero) digits is 41472, while the sum is 39.

The square root of 81806439 is about 9044.6912053425. The cubic root of 81806439 is about 434.1060409689.

The spelling of 81806439 in words is "eighty-one million, eight hundred six thousand, four hundred thirty-nine".