21111011021 has 2 divisors, whose sum is σ = 21111011022. Its totient is φ = 21111011020.

The previous prime is 21111010981. The next prime is 21111011023. The reversal of 21111011021 is 12011011112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15968113225 + 5142897796 = 126365^2 + 71714^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111011021 - 2⁶ = 21111010957 is a prime.

It is a Sophie Germain prime.

Together with 21111011023, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21111010993 and 21111011011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111011023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555505510 + 10555505511.

It is an arithmetic number, because the mean of its divisors is an integer number (10555505511).

Almost surely, 2^21111011021 is an apocalyptic number.

It is an amenable number.

21111011021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111011021 is an equidigital number, since it uses as much as digits as its factorization.

21111011021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4, while the sum is 11.

Adding to 21111011021 its reverse (12011011112), we get a palindrome (33122022133).

Subtracting from 21111011021 its reverse (12011011112), we obtain a palindrome (9099999909).

The spelling of 21111011021 in words is "twenty-one billion, one hundred eleven million, eleven thousand, twenty-one".