21210212221 has 32 divisors (see below), whose sum is σ = 24745420800. Its totient is φ = 17976816000.

The previous prime is 21210212171. The next prime is 21210212237. The reversal of 21210212221 is 12221201212.

It is a happy number.

It is not a de Polignac number, because 21210212221 - 2¹⁷ = 21210081149 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210212195 and 21210212204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210212521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5463201 + ... + 5467081.

It is an arithmetic number, because the mean of its divisors is an integer number (773294400).

Almost surely, 2^21210212221 is an apocalyptic number.

It is an amenable number.

21210212221 is a deficient number, since it is larger than the sum of its proper divisors (3535208579).

21210212221 is a wasteful number, since it uses less digits than its factorization.

21210212221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4321.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21210212221 its reverse (12221201212), we get a palindrome (33431413433).

The spelling of 21210212221 in words is "twenty-one billion, two hundred ten million, two hundred twelve thousand, two hundred twenty-one".