81209456617 has 2 divisors, whose sum is σ = 81209456618. Its totient is φ = 81209456616.

The previous prime is 81209456609. The next prime is 81209456663. The reversal of 81209456617 is 71665490218.

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., 60262394256 + 20947062361 = 245484^2 + 144731^2 .

It is a cyclic number.

It is not a de Polignac number, because 81209456617 - 2³ = 81209456609 is a prime.

It is not a weakly prime, because it can be changed into another prime (81209456417) 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, 40604728308 + 40604728309.

It is an arithmetic number, because the mean of its divisors is an integer number (40604728309).

Almost surely, 2^81209456617 is an apocalyptic number.

It is an amenable number.

81209456617 is a deficient number, since it is larger than the sum of its proper divisors (1).

81209456617 is an equidigital number, since it uses as much as digits as its factorization.

81209456617 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 725760, while the sum is 49.

The spelling of 81209456617 in words is "eighty-one billion, two hundred nine million, four hundred fifty-six thousand, six hundred seventeen".