21353165 has 4 divisors (see below), whose sum is σ = 25623804. Its totient is φ = 17082528.

The previous prime is 21353159. The next prime is 21353191. The reversal of 21353165 is 56135312.

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 2569609 + 18783556 = 1603^2 + 4334^2 .

It is a cyclic number.

It is not a de Polignac number, because 21353165 - 2²⁰ = 20304589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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, 2135312 + ... + 2135321.

It is an arithmetic number, because the mean of its divisors is an integer number (6405951).

Almost surely, 2^21353165 is an apocalyptic number.

It is an amenable number.

21353165 is a deficient number, since it is larger than the sum of its proper divisors (4270639).

21353165 is an equidigital number, since it uses as much as digits as its factorization.

21353165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4270638.

The product of its digits is 2700, while the sum is 26.

The square root of 21353165 is about 4620.9484957095. The cubic root of 21353165 is about 277.4304238090.

Adding to 21353165 its reverse (56135312), we get a palindrome (77488477).

The spelling of 21353165 in words is "twenty-one million, three hundred fifty-three thousand, one hundred sixty-five".