81950489681 has 2 divisors, whose sum is σ = 81950489682. Its totient is φ = 81950489680.

The previous prime is 81950489659. The next prime is 81950489743. The reversal of 81950489681 is 18698405918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65525760400 + 16424729281 = 255980^2 + 128159^2 .

It is a cyclic number.

It is not a de Polignac number, because 81950489681 - 2³⁰ = 80876747857 is a prime.

It is a super-2 number, since 2×81950489681² (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 81950489681.

It is not a weakly prime, because it can be changed into another prime (81950489281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40975244840 + 40975244841.

It is an arithmetic number, because the mean of its divisors is an integer number (40975244841).

Almost surely, 2^81950489681 is an apocalyptic number.

It is an amenable number.

81950489681 is a deficient number, since it is larger than the sum of its proper divisors (1).

81950489681 is an equidigital number, since it uses as much as digits as its factorization.

81950489681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4976640, while the sum is 59.

The spelling of 81950489681 in words is "eighty-one billion, nine hundred fifty million, four hundred eighty-nine thousand, six hundred eighty-one".