21212212212221 has 4 divisors (see below), whose sum is σ = 21352690438944. Its totient is φ = 21071733985500.

The previous prime is 21212212212211. The next prime is 21212212212239. The reversal of 21212212212221 is 12221221221212.

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-21212212212221 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212212212211) 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, 70239113135 + ... + 70239113436.

It is an arithmetic number, because the mean of its divisors is an integer number (5338172609736).

Almost surely, 2^{21212212212221} is an apocalyptic number.

It is an amenable number.

21212212212221 is a deficient number, since it is larger than the sum of its proper divisors (140478226723).

21212212212221 is a wasteful number, since it uses less digits than its factorization.

21212212212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140478226722.

The product of its digits is 512, while the sum is 23.

Adding to 21212212212221 its reverse (12221221221212), we get a palindrome (33433433433433).

The spelling of 21212212212221 in words is "twenty-one trillion, two hundred twelve billion, two hundred twelve million, two hundred twelve thousand, two hundred twenty-one".