81641065577 has 2 divisors, whose sum is σ = 81641065578. Its totient is φ = 81641065576.

The previous prime is 81641065567. The next prime is 81641065613. The reversal of 81641065577 is 77556014618.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 72833055376 + 8808010201 = 269876^2 + 93851^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81641065577 is a prime.

It is not a weakly prime, because it can be changed into another prime (81641065537) 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, 40820532788 + 40820532789.

It is an arithmetic number, because the mean of its divisors is an integer number (40820532789).

Almost surely, 2^81641065577 is an apocalyptic number.

It is an amenable number.

81641065577 is a deficient number, since it is larger than the sum of its proper divisors (1).

81641065577 is an equidigital number, since it uses as much as digits as its factorization.

81641065577 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1411200, while the sum is 50.

The spelling of 81641065577 in words is "eighty-one billion, six hundred forty-one million, sixty-five thousand, five hundred seventy-seven".