165998309 has 2 divisors, whose sum is σ = 165998310. Its totient is φ = 165998308.

The previous prime is 165998303. The next prime is 165998311. The reversal of 165998309 is 903899561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 150749284 + 15249025 = 12278^2 + 3905^2 .

It is a cyclic number.

It is not a de Polignac number, because 165998309 - 2⁴ = 165998293 is a prime.

It is a Sophie Germain prime.

Together with 165998311, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165998303) 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, 82999154 + 82999155.

It is an arithmetic number, because the mean of its divisors is an integer number (82999155).

Almost surely, 2^165998309 is an apocalyptic number.

It is an amenable number.

165998309 is a deficient number, since it is larger than the sum of its proper divisors (1).

165998309 is an equidigital number, since it uses as much as digits as its factorization.

165998309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 524880, while the sum is 50.

The square root of 165998309 is about 12884.0331030311. The cubic root of 165998309 is about 549.5845998371.

The spelling of 165998309 in words is "one hundred sixty-five million, nine hundred ninety-eight thousand, three hundred nine".