21210011221 has 4 divisors (see below), whose sum is σ = 24240012832. Its totient is φ = 18180009612.

The previous prime is 21210011153. The next prime is 21210011279. The reversal of 21210011221 is 12211001212.

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 21210011221 - 2⁷ = 21210011093 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210017221) 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, 1515000795 + ... + 1515000808.

It is an arithmetic number, because the mean of its divisors is an integer number (6060003208).

Almost surely, 2^21210011221 is an apocalyptic number.

It is an amenable number.

21210011221 is a deficient number, since it is larger than the sum of its proper divisors (3030001611).

21210011221 is an equidigital number, since it uses as much as digits as its factorization.

21210011221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3030001610.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21210011221 its reverse (12211001212), we get a palindrome (33421012433).

The spelling of 21210011221 in words is "twenty-one billion, two hundred ten million, eleven thousand, two hundred twenty-one".