21112222121 has 2 divisors, whose sum is σ = 21112222122. Its totient is φ = 21112222120.

The previous prime is 21112222081. The next prime is 21112222141. The reversal of 21112222121 is 12122221112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18168074521 + 2944147600 = 134789^2 + 54260^2 .

It is a cyclic number.

It is not a de Polignac number, because 21112222121 - 2²² = 21108027817 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21112222121.

It is not a weakly prime, because it can be changed into another prime (21112222141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556111060 + 10556111061.

It is an arithmetic number, because the mean of its divisors is an integer number (10556111061).

Almost surely, 2^21112222121 is an apocalyptic number.

It is an amenable number.

21112222121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112222121 is an equidigital number, since it uses as much as digits as its factorization.

21112222121 is an evil number, because the sum of its binary digits is even.

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

Adding to 21112222121 its reverse (12122221112), we get a palindrome (33234443233).

The spelling of 21112222121 in words is "twenty-one billion, one hundred twelve million, two hundred twenty-two thousand, one hundred twenty-one".