81271342561 has 2 divisors, whose sum is σ = 81271342562. Its totient is φ = 81271342560.

The previous prime is 81271342543. The next prime is 81271342591. The reversal of 81271342561 is 16524317218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41573171025 + 39698171536 = 203895^2 + 199244^2 .

It is a cyclic number.

It is not a de Polignac number, because 81271342561 - 2⁹ = 81271342049 is a prime.

It is a super-2 number, since 2×81271342561² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81271342531) 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 as a sum of consecutive naturals, namely, 40635671280 + 40635671281.

It is an arithmetic number, because the mean of its divisors is an integer number (40635671281).

Almost surely, 2^81271342561 is an apocalyptic number.

It is an amenable number.

81271342561 is a deficient number, since it is larger than the sum of its proper divisors (1).

81271342561 is an equidigital number, since it uses as much as digits as its factorization.

81271342561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80640, while the sum is 40.

Adding to 81271342561 its reverse (16524317218), we get a palindrome (97795659779).

The spelling of 81271342561 in words is "eighty-one billion, two hundred seventy-one million, three hundred forty-two thousand, five hundred sixty-one".