81318681 has 8 divisors (see below), whose sum is σ = 120472160. Its totient is φ = 54212436.

The previous prime is 81318659. The next prime is 81318709. The reversal of 81318681 is 18681318.

It is not a de Polignac number, because 81318681 - 2⁶ = 81318617 is a prime.

It is a super-2 number, since 2×81318681² = 13225455759159522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81318781) 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 7 ways as a sum of consecutive naturals, for example, 1505875 + ... + 1505928.

It is an arithmetic number, because the mean of its divisors is an integer number (15059020).

Almost surely, 2^81318681 is an apocalyptic number.

It is an amenable number.

81318681 is a deficient number, since it is larger than the sum of its proper divisors (39153479).

81318681 is a wasteful number, since it uses less digits than its factorization.

81318681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3011812 (or 3011806 counting only the distinct ones).

The product of its digits is 9216, while the sum is 36.

The square root of 81318681 is about 9017.6871203208. The cubic root of 81318681 is about 433.2415576188.

Adding to 81318681 its reverse (18681318), we get a palindrome (99999999).

The spelling of 81318681 in words is "eighty-one million, three hundred eighteen thousand, six hundred eighty-one".