21122212221 has 12 divisors (see below), whose sum is σ = 33283486080. Its totient is φ = 12801340680.

The previous prime is 21122212217. The next prime is 21122212231. The reversal of 21122212221 is 12221222112.

It is a happy number.

21122212221 is a `hidden beast` number, since 211 + 22 + 212 + 221 = 666.

It is not a de Polignac number, because 21122212221 - 2² = 21122212217 is a prime.

It is a super-2 number, since 2×21122212221² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21122212194 and 21122212203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122212231) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 106677741 + ... + 106677938.

It is an arithmetic number, because the mean of its divisors is an integer number (2773623840).

Almost surely, 2^21122212221 is an apocalyptic number.

It is an amenable number.

21122212221 is a deficient number, since it is larger than the sum of its proper divisors (12161273859).

21122212221 is a wasteful number, since it uses less digits than its factorization.

21122212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213355696 (or 213355693 counting only the distinct ones).

The product of its digits is 128, while the sum is 18.

Adding to 21122212221 its reverse (12221222112), we get a palindrome (33343434333).

The spelling of 21122212221 in words is "twenty-one billion, one hundred twenty-two million, two hundred twelve thousand, two hundred twenty-one".