21335221 has 4 divisors (see below), whose sum is σ = 22590252. Its totient is φ = 20080192.

The previous prime is 21335219. The next prime is 21335231. The reversal of 21335221 is 12253312.

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 15760900 + 5574321 = 3970^2 + 2361^2 .

It is a cyclic number.

It is not a de Polignac number, because 21335221 - 2¹ = 21335219 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 (21335231) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 627490 + ... + 627523.

It is an arithmetic number, because the mean of its divisors is an integer number (5647563).

Almost surely, 2^21335221 is an apocalyptic number.

It is an amenable number.

21335221 is a deficient number, since it is larger than the sum of its proper divisors (1255031).

21335221 is a wasteful number, since it uses less digits than its factorization.

21335221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1255030.

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

The square root of 21335221 is about 4619.0064949078. The cubic root of 21335221 is about 277.3526897175.

Adding to 21335221 its reverse (12253312), we get a palindrome (33588533).

The spelling of 21335221 in words is "twenty-one million, three hundred thirty-five thousand, two hundred twenty-one".