21333221 has 8 divisors (see below), whose sum is σ = 26256384. Its totient is φ = 16878960.

The previous prime is 21333199. The next prime is 21333251. The reversal of 21333221 is 12233312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21333221 - 2²² = 17138917 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21333221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21333251) 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 7 ways as a sum of consecutive naturals, for example, 117125 + ... + 117306.

It is an arithmetic number, because the mean of its divisors is an integer number (3282048).

It is a self-describing number.

Almost surely, 2^21333221 is an apocalyptic number.

It is an amenable number.

21333221 is a deficient number, since it is larger than the sum of its proper divisors (4923163).

21333221 is a wasteful number, since it uses less digits than its factorization.

21333221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 234451.

The product of its digits is 216, while the sum is 17.

The square root of 21333221 is about 4618.7899930610. The cubic root of 21333221 is about 277.3440229420.

Adding to 21333221 its reverse (12233312), we get a palindrome (33566533).

Subtracting from 21333221 its reverse (12233312), we obtain a palindrome (9099909).

The spelling of 21333221 in words is "twenty-one million, three hundred thirty-three thousand, two hundred twenty-one".