21223205 has 4 divisors (see below), whose sum is σ = 25467852. Its totient is φ = 16978560.

The previous prime is 21223193. The next prime is 21223219. The reversal of 21223205 is 50232212.

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 5997601 + 15225604 = 2449^2 + 3902^2 .

It is not a de Polignac number, because 21223205 - 2⁶ = 21223141 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, 2122316 + ... + 2122325.

It is an arithmetic number, because the mean of its divisors is an integer number (6366963).

Almost surely, 2^21223205 is an apocalyptic number.

It is an amenable number.

21223205 is a deficient number, since it is larger than the sum of its proper divisors (4244647).

21223205 is an equidigital number, since it uses as much as digits as its factorization.

21223205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4244646.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21223205 is about 4606.8649860833. The cubic root of 21223205 is about 276.8664441506.

Adding to 21223205 its reverse (50232212), we get a palindrome (71455417).

The spelling of 21223205 in words is "twenty-one million, two hundred twenty-three thousand, two hundred five".