165921891 has 32 divisors (see below), whose sum is σ = 233127936. Its totient is φ = 104880000.

The previous prime is 165921869. The next prime is 165921911. The reversal of 165921891 is 198129561.

165921891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 165921891 - 2⁵ = 165921859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (165921841) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 868606 + ... + 868796.

It is an arithmetic number, because the mean of its divisors is an integer number (7285248).

Almost surely, 2^165921891 is an apocalyptic number.

165921891 is a deficient number, since it is larger than the sum of its proper divisors (67206045).

165921891 is a wasteful number, since it uses less digits than its factorization.

165921891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 403.

The product of its digits is 38880, while the sum is 42.

The square root of 165921891 is about 12881.0671529963. The cubic root of 165921891 is about 549.5002523869.

The spelling of 165921891 in words is "one hundred sixty-five million, nine hundred twenty-one thousand, eight hundred ninety-one".