81856207 has 4 divisors (see below), whose sum is σ = 86671296. Its totient is φ = 77041120.

The previous prime is 81856169. The next prime is 81856223. The reversal of 81856207 is 70265818.

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

It is a cyclic number.

It is not a de Polignac number, because 81856207 - 2⁷ = 81856079 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 (81856277) 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, 2407519 + ... + 2407552.

It is an arithmetic number, because the mean of its divisors is an integer number (21667824).

Almost surely, 2^81856207 is an apocalyptic number.

81856207 is a deficient number, since it is larger than the sum of its proper divisors (4815089).

81856207 is a wasteful number, since it uses less digits than its factorization.

81856207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4815088.

The product of its (nonzero) digits is 26880, while the sum is 37.

The square root of 81856207 is about 9047.4420141828. The cubic root of 81856207 is about 434.1940544556.

The spelling of 81856207 in words is "eighty-one million, eight hundred fifty-six thousand, two hundred seven".