81115518 has 16 divisors (see below), whose sum is σ = 176979456. Its totient is φ = 24580440.

The previous prime is 81115513. The next prime is 81115547. The reversal of 81115518 is 81551118.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81115513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 614446 + ... + 614577.

It is an arithmetic number, because the mean of its divisors is an integer number (11061216).

Almost surely, 2^81115518 is an apocalyptic number.

81115518 is an abundant number, since it is smaller than the sum of its proper divisors (95863938).

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

81115518 is a wasteful number, since it uses less digits than its factorization.

81115518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1229039.

The product of its digits is 1600, while the sum is 30.

The square root of 81115518 is about 9006.4153801610. The cubic root of 81115518 is about 432.8804595454.

Subtracting 81115518 from its reverse (81551118), we obtain a square (435600 = 660²).

The spelling of 81115518 in words is "eighty-one million, one hundred fifteen thousand, five hundred eighteen".