165638221 has 4 divisors (see below), whose sum is σ = 189300832. Its totient is φ = 141975612.

The previous prime is 165638183. The next prime is 165638251. The reversal of 165638221 is 122836561.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 165638221 - 2¹¹ = 165636173 is a prime.

It is a super-3 number, since 3×165638221³ (a number of 26 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165638251) 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, 11831295 + ... + 11831308.

It is an arithmetic number, because the mean of its divisors is an integer number (47325208).

Almost surely, 2^165638221 is an apocalyptic number.

It is an amenable number.

165638221 is a deficient number, since it is larger than the sum of its proper divisors (23662611).

165638221 is an equidigital number, since it uses as much as digits as its factorization.

165638221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23662610.

The product of its digits is 17280, while the sum is 34.

The square root of 165638221 is about 12870.0513207990. The cubic root of 165638221 is about 549.1869209107.

The spelling of 165638221 in words is "one hundred sixty-five million, six hundred thirty-eight thousand, two hundred twenty-one".