165406121 has 4 divisors (see below), whose sum is σ = 165543252. Its totient is φ = 165268992.

The previous prime is 165406103. The next prime is 165406127. The reversal of 165406121 is 121604561.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 92064025 + 73342096 = 9595^2 + 8564^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-165406121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165406127) 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 in 3 ways as a sum of consecutive naturals, for example, 66740 + ... + 69173.

It is an arithmetic number, because the mean of its divisors is an integer number (41385813).

Almost surely, 2^165406121 is an apocalyptic number.

It is an amenable number.

165406121 is a deficient number, since it is larger than the sum of its proper divisors (137131).

165406121 is a wasteful number, since it uses less digits than its factorization.

165406121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137130.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 165406121 is about 12861.0311017430. The cubic root of 165406121 is about 548.9302855617.

The spelling of 165406121 in words is "one hundred sixty-five million, four hundred six thousand, one hundred twenty-one".