165158721 has 48 divisors (see below), whose sum is σ = 294927360. Its totient is φ = 86728320.

The previous prime is 165158717. The next prime is 165158729. The reversal of 165158721 is 127851561.

165158721 is a `hidden beast` number, since 1 + 6 + 51 + 587 + 21 = 666.

It is not a de Polignac number, because 165158721 - 2² = 165158717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (165158729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 344560 + ... + 345038.

It is an arithmetic number, because the mean of its divisors is an integer number (6144320).

Almost surely, 2^165158721 is an apocalyptic number.

It is an amenable number.

165158721 is a deficient number, since it is larger than the sum of its proper divisors (129768639).

165158721 is a wasteful number, since it uses less digits than its factorization.

165158721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 926 (or 923 counting only the distinct ones).

The product of its digits is 16800, while the sum is 36.

The square root of 165158721 is about 12851.4093001507. The cubic root of 165158721 is about 548.6564683722.

The spelling of 165158721 in words is "one hundred sixty-five million, one hundred fifty-eight thousand, seven hundred twenty-one".