21112212221 has 4 divisors (see below), whose sum is σ = 21123795072. Its totient is φ = 21100629372.

The previous prime is 21112212169. The next prime is 21112212223. The reversal of 21112212221 is 12221221112.

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 a de Polignac number, because none of the positive numbers 2^k-21112212221 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 21112212221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21112212223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5788691 + ... + 5792336.

It is an arithmetic number, because the mean of its divisors is an integer number (5280948768).

Almost surely, 2^21112212221 is an apocalyptic number.

It is an amenable number.

21112212221 is a deficient number, since it is larger than the sum of its proper divisors (11582851).

21112212221 is a wasteful number, since it uses less digits than its factorization.

21112212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11582850.

The product of its digits is 64, while the sum is 17.

Adding to 21112212221 its reverse (12221221112), we get a palindrome (33333433333).

The spelling of 21112212221 in words is "twenty-one billion, one hundred twelve million, two hundred twelve thousand, two hundred twenty-one".