21321165 has 16 divisors (see below), whose sum is σ = 34171200. Its totient is φ = 11352192.

The previous prime is 21321133. The next prime is 21321169. The reversal of 21321165 is 56112312.

It is not a de Polignac number, because 21321165 - 2⁵ = 21321133 is a prime.

It is a Curzon number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321169) 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 15 ways as a sum of consecutive naturals, for example, 16306 + ... + 17564.

It is an arithmetic number, because the mean of its divisors is an integer number (2135700).

Almost surely, 2^21321165 is an apocalyptic number.

It is an amenable number.

21321165 is a deficient number, since it is larger than the sum of its proper divisors (12850035).

21321165 is a wasteful number, since it uses less digits than its factorization.

21321165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2396.

The product of its digits is 360, while the sum is 21.

The square root of 21321165 is about 4617.4847049016. The cubic root of 21321165 is about 277.2917681418.

Adding to 21321165 its reverse (56112312), we get a palindrome (77433477).

The spelling of 21321165 in words is "twenty-one million, three hundred twenty-one thousand, one hundred sixty-five".