21112111021 has 2 divisors, whose sum is σ = 21112111022. Its totient is φ = 21112111020.

The previous prime is 21112111019. The next prime is 21112111051. The reversal of 21112111021 is 12011121112.

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., 17772889225 + 3339221796 = 133315^2 + 57786^2 .

It is a cyclic number.

It is not a de Polignac number, because 21112111021 - 2¹ = 21112111019 is a prime.

Together with 21112111019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21112110992 and 21112111010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21112111051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556055510 + 10556055511.

It is an arithmetic number, because the mean of its divisors is an integer number (10556055511).

Almost surely, 2^21112111021 is an apocalyptic number.

It is an amenable number.

21112111021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112111021 is an equidigital number, since it uses as much as digits as its factorization.

21112111021 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 21112111021 its reverse (12011121112), we get a palindrome (33123232133).

The spelling of 21112111021 in words is "twenty-one billion, one hundred twelve million, one hundred eleven thousand, twenty-one".