21212111222221 has 4 divisors (see below), whose sum is σ = 21467678827392. Its totient is φ = 20956543617052.

The previous prime is 21212111222201. The next prime is 21212111222243. The reversal of 21212111222221 is 12222211121212.

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 21212111222221 - 2⁹ = 21212111221709 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21212111222192 and 21212111222201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212111222201) 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, 127783802461 + ... + 127783802626.

It is an arithmetic number, because the mean of its divisors is an integer number (5366919706848).

Almost surely, 2^{21212111222221} is an apocalyptic number.

It is an amenable number.

21212111222221 is a deficient number, since it is larger than the sum of its proper divisors (255567605171).

21212111222221 is an equidigital number, since it uses as much as digits as its factorization.

21212111222221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255567605170.

The product of its digits is 256, while the sum is 22.

Adding to 21212111222221 its reverse (12222211121212), we get a palindrome (33434322343433).

The spelling of 21212111222221 in words is "twenty-one trillion, two hundred twelve billion, one hundred eleven million, two hundred twenty-two thousand, two hundred twenty-one".