81606765169 has 2 divisors, whose sum is σ = 81606765170. Its totient is φ = 81606765168.

The previous prime is 81606765137. The next prime is 81606765181. The reversal of 81606765169 is 96156760618.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80776460944 + 830304225 = 284212^2 + 28815^2 .

It is a cyclic number.

It is not a de Polignac number, because 81606765169 - 2⁵ = 81606765137 is a prime.

It is a super-2 number, since 2×81606765169² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81606766169) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40803382584 + 40803382585.

It is an arithmetic number, because the mean of its divisors is an integer number (40803382585).

Almost surely, 2^81606765169 is an apocalyptic number.

It is an amenable number.

81606765169 is a deficient number, since it is larger than the sum of its proper divisors (1).

81606765169 is an equidigital number, since it uses as much as digits as its factorization.

81606765169 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3265920, while the sum is 55.

The spelling of 81606765169 in words is "eighty-one billion, six hundred six million, seven hundred sixty-five thousand, one hundred sixty-nine".