165669721 has 16 divisors (see below), whose sum is σ = 206179200. Its totient is φ = 129886848.

The previous prime is 165669703. The next prime is 165669727. The reversal of 165669721 is 127966561.

It is not a de Polignac number, because 165669721 - 2¹¹ = 165667673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165669727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17620 + ... + 25333.

It is an arithmetic number, because the mean of its divisors is an integer number (12886200).

Almost surely, 2^165669721 is an apocalyptic number.

It is an amenable number.

165669721 is a deficient number, since it is larger than the sum of its proper divisors (40509479).

165669721 is a wasteful number, since it uses less digits than its factorization.

165669721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43008.

The product of its digits is 136080, while the sum is 43.

The square root of 165669721 is about 12871.2750339661. The cubic root of 165669721 is about 549.2217323035.

The spelling of 165669721 in words is "one hundred sixty-five million, six hundred sixty-nine thousand, seven hundred twenty-one".