21011223221 has 4 divisors (see below), whose sum is σ = 21020868000. Its totient is φ = 21001578444.

The previous prime is 21011223217. The next prime is 21011223271. The reversal of 21011223221 is 12232211012.

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 21011223221 - 2² = 21011223217 is a prime.

It is a super-2 number, since 2×21011223221² (a number of 21 digits) contains 22 as substring.

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 21011223221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011223271) 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 3 ways as a sum of consecutive naturals, for example, 4819121 + ... + 4823478.

It is an arithmetic number, because the mean of its divisors is an integer number (5255217000).

Almost surely, 2^21011223221 is an apocalyptic number.

It is an amenable number.

21011223221 is a deficient number, since it is larger than the sum of its proper divisors (9644779).

21011223221 is an equidigital number, since it uses as much as digits as its factorization.

21011223221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9644778.

The product of its (nonzero) digits is 96, while the sum is 17.

Adding to 21011223221 its reverse (12232211012), we get a palindrome (33243434233).

The spelling of 21011223221 in words is "twenty-one billion, eleven million, two hundred twenty-three thousand, two hundred twenty-one".