81856766 has 4 divisors (see below), whose sum is σ = 122785152. Its totient is φ = 40928382.

The previous prime is 81856759. The next prime is 81856811. The reversal of 81856766 is 66765818.

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

It is a self number, because there is not a number n which added to its sum of digits gives 81856766.

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 20464190 + ... + 20464193.

It is an arithmetic number, because the mean of its divisors is an integer number (30696288).

Almost surely, 2^81856766 is an apocalyptic number.

81856766 is a deficient number, since it is larger than the sum of its proper divisors (40928386).

81856766 is a wasteful number, since it uses less digits than its factorization.

81856766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40928385.

The product of its digits is 483840, while the sum is 47.

The square root of 81856766 is about 9047.4729068398. The cubic root of 81856766 is about 434.1950428307.

The spelling of 81856766 in words is "eighty-one million, eight hundred fifty-six thousand, seven hundred sixty-six".