165811957 has 4 divisors (see below), whose sum is σ = 166071276. Its totient is φ = 165552640.

The previous prime is 165811951. The next prime is 165811973. The reversal of 165811957 is 759118561.

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 140801956 + 25010001 = 11866^2 + 5001^2 .

It is a cyclic number.

It is not a de Polignac number, because 165811957 - 2³ = 165811949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165811951) 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, 128698 + ... + 129979.

It is an arithmetic number, because the mean of its divisors is an integer number (41517819).

Almost surely, 2^165811957 is an apocalyptic number.

It is an amenable number.

165811957 is a deficient number, since it is larger than the sum of its proper divisors (259319).

165811957 is an equidigital number, since it uses as much as digits as its factorization.

165811957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 259318.

The product of its digits is 75600, while the sum is 43.

The square root of 165811957 is about 12876.7991752609. The cubic root of 165811957 is about 549.3788657375.

The spelling of 165811957 in words is "one hundred sixty-five million, eight hundred eleven thousand, nine hundred fifty-seven".