165156721 has 16 divisors (see below), whose sum is σ = 183997440. Its totient is φ = 147525840.

The previous prime is 165156713. The next prime is 165156727. The reversal of 165156721 is 127651561.

165156721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 165156721 - 2³ = 165156713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165156727) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28366 + ... + 33688.

It is an arithmetic number, because the mean of its divisors is an integer number (11499840).

Almost surely, 2^165156721 is an apocalyptic number.

It is an amenable number.

165156721 is a deficient number, since it is larger than the sum of its proper divisors (18840719).

165156721 is a wasteful number, since it uses less digits than its factorization.

165156721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5436.

The product of its digits is 12600, while the sum is 34.

The square root of 165156721 is about 12851.3314874374. The cubic root of 165156721 is about 548.6542536998.

The spelling of 165156721 in words is "one hundred sixty-five million, one hundred fifty-six thousand, seven hundred twenty-one".