21243211221 has 4 divisors (see below), whose sum is σ = 28324281632. Its totient is φ = 14162140812.

The previous prime is 21243211219. The next prime is 21243211229. The reversal of 21243211221 is 12211234212.

It is a happy number.

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 not a de Polignac number, because 21243211221 - 2¹ = 21243211219 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 (21243211229) 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, 3540535201 + ... + 3540535206.

It is an arithmetic number, because the mean of its divisors is an integer number (7081070408).

Almost surely, 2^21243211221 is an apocalyptic number.

It is an amenable number.

21243211221 is a deficient number, since it is larger than the sum of its proper divisors (7081070411).

21243211221 is an equidigital number, since it uses as much as digits as its factorization.

21243211221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7081070410.

The product of its digits is 384, while the sum is 21.

Adding to 21243211221 its reverse (12211234212), we get a palindrome (33454445433).

The spelling of 21243211221 in words is "twenty-one billion, two hundred forty-three million, two hundred eleven thousand, two hundred twenty-one".