81268816609 has 2 divisors, whose sum is σ = 81268816610. Its totient is φ = 81268816608.

The previous prime is 81268816589. The next prime is 81268816621. The reversal of 81268816609 is 90661886218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61055939025 + 20212877584 = 247095^2 + 142172^2 .

It is a cyclic number.

It is not a de Polignac number, because 81268816609 - 2¹³ = 81268808417 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81268816609.

It is not a weakly prime, because it can be changed into another prime (81268816639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40634408304 + 40634408305.

It is an arithmetic number, because the mean of its divisors is an integer number (40634408305).

Almost surely, 2^81268816609 is an apocalyptic number.

It is an amenable number.

81268816609 is a deficient number, since it is larger than the sum of its proper divisors (1).

81268816609 is an equidigital number, since it uses as much as digits as its factorization.

81268816609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1990656, while the sum is 55.

The spelling of 81268816609 in words is "eighty-one billion, two hundred sixty-eight million, eight hundred sixteen thousand, six hundred nine".