21111102121 has 2 divisors, whose sum is σ = 21111102122. Its totient is φ = 21111102120.

The previous prime is 21111102119. The next prime is 21111102149. The reversal of 21111102121 is 12120111112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21107731225 + 3370896 = 145285^2 + 1836^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111102121 - 2¹ = 21111102119 is a prime.

Together with 21111102119, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21111102191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555551060 + 10555551061.

It is an arithmetic number, because the mean of its divisors is an integer number (10555551061).

Almost surely, 2^21111102121 is an apocalyptic number.

It is an amenable number.

21111102121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111102121 is an equidigital number, since it uses as much as digits as its factorization.

21111102121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21111102121 its reverse (12120111112), we get a palindrome (33231213233).

The spelling of 21111102121 in words is "twenty-one billion, one hundred eleven million, one hundred two thousand, one hundred twenty-one".