81566266519 has 2 divisors, whose sum is σ = 81566266520. Its totient is φ = 81566266518.

The previous prime is 81566266511. The next prime is 81566266531. The reversal of 81566266519 is 91566266518.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81566266519 - 2³ = 81566266511 is a prime.

It is a super-2 number, since 2×81566266519² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81566266519.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81566266511) 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 as a sum of consecutive naturals, namely, 40783133259 + 40783133260.

It is an arithmetic number, because the mean of its divisors is an integer number (40783133260).

Almost surely, 2^81566266519 is an apocalyptic number.

81566266519 is a deficient number, since it is larger than the sum of its proper divisors (1).

81566266519 is an equidigital number, since it uses as much as digits as its factorization.

81566266519 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4665600, while the sum is 55.

Subtracting 81566266519 from its reverse (91566266518), we obtain a palindrome (9999999999).

The spelling of 81566266519 in words is "eighty-one billion, five hundred sixty-six million, two hundred sixty-six thousand, five hundred nineteen".