81581218518 has 32 divisors (see below), whose sum is σ = 164645913600. Its totient is φ = 26946609536.

The previous prime is 81581218513. The next prime is 81581218561.

81581218518 is nontrivially palindromic in base 10.

It is a super-2 number, since 2×81581218518² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81581218513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3404503 + ... + 3428381.

It is an arithmetic number, because the mean of its divisors is an integer number (5145184800).

Almost surely, 2^81581218518 is an apocalyptic number.

81581218518 is an abundant number, since it is smaller than the sum of its proper divisors (83064695082).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81581218518 is a wasteful number, since it uses less digits than its factorization.

81581218518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29036.

The product of its digits is 204800, while the sum is 48.

The spelling of 81581218518 in words is "eighty-one billion, five hundred eighty-one million, two hundred eighteen thousand, five hundred eighteen".