81566518 has 32 divisors (see below), whose sum is σ = 138700800. Its totient is φ = 35640000.

The previous prime is 81566509. The next prime is 81566519.

81566518 is nontrivially palindromic in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81566519) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 135418 + ... + 136018.

It is an arithmetic number, because the mean of its divisors is an integer number (4334400).

Almost surely, 2^81566518 is an apocalyptic number.

81566518 is a deficient number, since it is larger than the sum of its proper divisors (57134282).

81566518 is a wasteful number, since it uses less digits than its factorization.

81566518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844.

The product of its digits is 57600, while the sum is 40.

The square root of 81566518 is about 9031.4183825133. The cubic root of 81566518 is about 433.6812449882.

The spelling of 81566518 in words is "eighty-one million, five hundred sixty-six thousand, five hundred eighteen".