165666121 has 2 divisors, whose sum is σ = 165666122. Its totient is φ = 165666120.

The previous prime is 165666119. The next prime is 165666133. The reversal of 165666121 is 121666561.

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., 157854096 + 7812025 = 12564^2 + 2795^2 .

It is a cyclic number.

It is not a de Polignac number, because 165666121 - 2¹ = 165666119 is a prime.

Together with 165666119, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (165666161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82833060 + 82833061.

It is an arithmetic number, because the mean of its divisors is an integer number (82833061).

Almost surely, 2^165666121 is an apocalyptic number.

It is an amenable number.

165666121 is a deficient number, since it is larger than the sum of its proper divisors (1).

165666121 is an equidigital number, since it uses as much as digits as its factorization.

165666121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 34.

The square root of 165666121 is about 12871.1351869212. The cubic root of 165666121 is about 549.2177540819.

The spelling of 165666121 in words is "one hundred sixty-five million, six hundred sixty-six thousand, one hundred twenty-one".