165018161921 has 4 divisors (see below), whose sum is σ = 165087123012. Its totient is φ = 164949200832.

The previous prime is 165018161881. The next prime is 165018161929. The reversal of 165018161921 is 129161810561.

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 46880910400 + 118137251521 = 216520^2 + 343711^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-165018161921 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (165018161929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34476956 + ... + 34481741.

It is an arithmetic number, because the mean of its divisors is an integer number (41271780753).

Almost surely, 2^165018161921 is an apocalyptic number.

It is an amenable number.

165018161921 is a deficient number, since it is larger than the sum of its proper divisors (68961091).

165018161921 is an equidigital number, since it uses as much as digits as its factorization.

165018161921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68961090.

The product of its (nonzero) digits is 25920, while the sum is 41.

The spelling of 165018161921 in words is "one hundred sixty-five billion, eighteen million, one hundred sixty-one thousand, nine hundred twenty-one".