165610021 has 4 divisors (see below), whose sum is σ = 166801600. Its totient is φ = 164418444.

The previous prime is 165609973. The next prime is 165610057. The reversal of 165610021 is 120016561.

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 165610021 - 2¹⁷ = 165478949 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 165609974 and 165610001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165610721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 595581 + ... + 595858.

It is an arithmetic number, because the mean of its divisors is an integer number (41700400).

Almost surely, 2^165610021 is an apocalyptic number.

It is an amenable number.

165610021 is a deficient number, since it is larger than the sum of its proper divisors (1191579).

165610021 is a wasteful number, since it uses less digits than its factorization.

165610021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1191578.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 165610021 is about 12868.9557074380. The cubic root of 165610021 is about 549.1557526814.

Adding to 165610021 its reverse (120016561), we get a palindrome (285626582).

The spelling of 165610021 in words is "one hundred sixty-five million, six hundred ten thousand, twenty-one".