165609221 has 2 divisors, whose sum is σ = 165609222. Its totient is φ = 165609220.

The previous prime is 165609217. The next prime is 165609233. The reversal of 165609221 is 122906561.

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., 104550625 + 61058596 = 10225^2 + 7814^2 .

It is a cyclic number.

It is not a de Polignac number, because 165609221 - 2² = 165609217 is a prime.

It is a Sophie Germain 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 (165609281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82804610 + 82804611.

It is an arithmetic number, because the mean of its divisors is an integer number (82804611).

Almost surely, 2^165609221 is an apocalyptic number.

It is an amenable number.

165609221 is a deficient number, since it is larger than the sum of its proper divisors (1).

165609221 is an equidigital number, since it uses as much as digits as its factorization.

165609221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 165609221 is about 12868.9246248473. The cubic root of 165609221 is about 549.1548684247.

The spelling of 165609221 in words is "one hundred sixty-five million, six hundred nine thousand, two hundred twenty-one".