21103030021 has 2 divisors, whose sum is σ = 21103030022. Its totient is φ = 21103030020.

The previous prime is 21103030001. The next prime is 21103030027. The reversal of 21103030021 is 12003030112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21058072996 + 44957025 = 145114^2 + 6705^2 .

It is a cyclic number.

It is not a de Polignac number, because 21103030021 - 2¹¹ = 21103027973 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21103029983 and 21103030010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21103030027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551515010 + 10551515011.

It is an arithmetic number, because the mean of its divisors is an integer number (10551515011).

Almost surely, 2^21103030021 is an apocalyptic number.

It is an amenable number.

21103030021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21103030021 is an equidigital number, since it uses as much as digits as its factorization.

21103030021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 13.

Adding to 21103030021 its reverse (12003030112), we get a palindrome (33106060133).

Subtracting from 21103030021 its reverse (12003030112), we obtain a palindrome (9099999909).

The spelling of 21103030021 in words is "twenty-one billion, one hundred three million, thirty thousand, twenty-one".