21353221 has 4 divisors (see below), whose sum is σ = 21715200. Its totient is φ = 20991244.

The previous prime is 21353219. The next prime is 21353243. The reversal of 21353221 is 12235312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21353221 - 2¹ = 21353219 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 (21353201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 180901 + ... + 181018.

It is an arithmetic number, because the mean of its divisors is an integer number (5428800).

Almost surely, 2^21353221 is an apocalyptic number.

It is an amenable number.

21353221 is a deficient number, since it is larger than the sum of its proper divisors (361979).

21353221 is an equidigital number, since it uses as much as digits as its factorization.

21353221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 361978.

The product of its digits is 360, while the sum is 19.

The square root of 21353221 is about 4620.9545550676. The cubic root of 21353221 is about 277.4306663350.

Adding to 21353221 its reverse (12235312), we get a palindrome (33588533).

It can be divided in two parts, 2135 and 3221, that added together give a triangular number (5356 = T₁₀₃).

The spelling of 21353221 in words is "twenty-one million, three hundred fifty-three thousand, two hundred twenty-one".