81566266511 has 2 divisors, whose sum is σ = 81566266512. Its totient is φ = 81566266510.

The previous prime is 81566266501. The next prime is 81566266519. The reversal of 81566266511 is 11566266518.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81566266511 is a prime.

It is a super-2 number, since 2×81566266511² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81566266519) 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, 40783133255 + 40783133256.

It is an arithmetic number, because the mean of its divisors is an integer number (40783133256).

Almost surely, 2^81566266511 is an apocalyptic number.

81566266511 is a deficient number, since it is larger than the sum of its proper divisors (1).

81566266511 is an equidigital number, since it uses as much as digits as its factorization.

81566266511 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 518400, while the sum is 47.

The spelling of 81566266511 in words is "eighty-one billion, five hundred sixty-six million, two hundred sixty-six thousand, five hundred eleven".