81256665218 has 8 divisors (see below), whose sum is σ = 121898063100. Its totient is φ = 40623977520.

The previous prime is 81256665211. The next prime is 81256665223.

81256665218 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in 2 ways, for example, as 74358199969 + 6898465249 = 272687^2 + 83057^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (81256665211) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2154173 + ... + 2191568.

Almost surely, 2^81256665218 is an apocalyptic number.

81256665218 is a deficient number, since it is larger than the sum of its proper divisors (40641397882).

81256665218 is a wasteful number, since it uses less digits than its factorization.

81256665218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4355092.

The product of its digits is 1382400, while the sum is 50.

The spelling of 81256665218 in words is "eighty-one billion, two hundred fifty-six million, six hundred sixty-five thousand, two hundred eighteen".