21304223 has 4 divisors (see below), whose sum is σ = 21991488. Its totient is φ = 20616960.

The previous prime is 21304219. The next prime is 21304237. The reversal of 21304223 is 32240312.

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 21304223 - 2² = 21304219 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21304253) 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, 343586 + ... + 343647.

It is an arithmetic number, because the mean of its divisors is an integer number (5497872).

Almost surely, 2^21304223 is an apocalyptic number.

21304223 is a deficient number, since it is larger than the sum of its proper divisors (687265).

21304223 is an equidigital number, since it uses as much as digits as its factorization.

21304223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 687264.

The product of its (nonzero) digits is 288, while the sum is 17.

The square root of 21304223 is about 4615.6497917411. The cubic root of 21304223 is about 277.2183024562.

Adding to 21304223 its reverse (32240312), we get a palindrome (53544535).

The spelling of 21304223 in words is "twenty-one million, three hundred four thousand, two hundred twenty-three".