21210222221 has 4 divisors (see below), whose sum is σ = 21557930844. Its totient is φ = 20862513600.

The previous prime is 21210222211. The next prime is 21210222259. The reversal of 21210222221 is 12222201212.

It is a happy number.

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 6093519721 + 15116702500 = 78061^2 + 122950^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210222221 - 2⁶ = 21210222157 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21210222221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210222211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 173854220 + ... + 173854341.

It is an arithmetic number, because the mean of its divisors is an integer number (5389482711).

Almost surely, 2^21210222221 is an apocalyptic number.

It is an amenable number.

21210222221 is a deficient number, since it is larger than the sum of its proper divisors (347708623).

21210222221 is an equidigital number, since it uses as much as digits as its factorization.

21210222221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 347708622.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21210222221 its reverse (12222201212), we get a palindrome (33432423433).

The spelling of 21210222221 in words is "twenty-one billion, two hundred ten million, two hundred twenty-two thousand, two hundred twenty-one".