165686681 has 2 divisors, whose sum is σ = 165686682. Its totient is φ = 165686680.

The previous prime is 165686671. The next prime is 165686693. The reversal of 165686681 is 186686561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 157276681 + 8410000 = 12541^2 + 2900^2 .

It is a cyclic number.

It is not a de Polignac number, because 165686681 - 2¹⁰ = 165685657 is a prime.

It is a super-2 number, since 2×165686681² = 54904152521591522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (165686671) 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, 82843340 + 82843341.

It is an arithmetic number, because the mean of its divisors is an integer number (82843341).

Almost surely, 2^165686681 is an apocalyptic number.

It is an amenable number.

165686681 is a deficient number, since it is larger than the sum of its proper divisors (1).

165686681 is an equidigital number, since it uses as much as digits as its factorization.

165686681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 414720, while the sum is 47.

The square root of 165686681 is about 12871.9338484938. The cubic root of 165686681 is about 549.2404733719.

The spelling of 165686681 in words is "one hundred sixty-five million, six hundred eighty-six thousand, six hundred eighty-one".