81566266518 has 32 divisors (see below), whose sum is σ = 197736405120. Its totient is φ = 24717050280.

The previous prime is 81566266511. The next prime is 81566266519.

81566266518 is a `hidden beast` number, since 8 + 1 + 5 + 6 + 62 + 66 + 518 = 666.

81566266518 is nontrivially palindromic in base 10.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81566266511) 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, 68657880 + ... + 68659067.

It is an arithmetic number, because the mean of its divisors is an integer number (6179262660).

Almost surely, 2^81566266518 is an apocalyptic number.

81566266518 is an abundant number, since it is smaller than the sum of its proper divisors (116170138602).

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

81566266518 is a wasteful number, since it uses less digits than its factorization.

81566266518 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137316969 (or 137316963 counting only the distinct ones).

The product of its digits is 4147200, while the sum is 54.

The spelling of 81566266518 in words is "eighty-one billion, five hundred sixty-six million, two hundred sixty-six thousand, five hundred eighteen".