21189215 has 4 divisors (see below), whose sum is σ = 25427064. Its totient is φ = 16951368.

The previous prime is 21189173. The next prime is 21189221. The reversal of 21189215 is 51298112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21189215 - 2²⁰ = 20140639 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, 2118917 + ... + 2118926.

It is an arithmetic number, because the mean of its divisors is an integer number (6356766).

Almost surely, 2^21189215 is an apocalyptic number.

21189215 is a deficient number, since it is larger than the sum of its proper divisors (4237849).

21189215 is an equidigital number, since it uses as much as digits as its factorization.

21189215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4237848.

The product of its digits is 1440, while the sum is 29.

The square root of 21189215 is about 4603.1744481390. The cubic root of 21189215 is about 276.7185601277.

The spelling of 21189215 in words is "twenty-one million, one hundred eighty-nine thousand, two hundred fifteen".