21100021021 has 2 divisors, whose sum is σ = 21100021022. Its totient is φ = 21100021020.

The previous prime is 21100021001. The next prime is 21100021027. The reversal of 21100021021 is 12012000112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20942141796 + 157879225 = 144714^2 + 12565^2 .

It is a cyclic number.

It is not a de Polignac number, because 21100021021 - 2¹⁵ = 21099988253 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21100020989 and 21100021007.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21100021027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550010510 + 10550010511.

It is an arithmetic number, because the mean of its divisors is an integer number (10550010511).

Almost surely, 2^21100021021 is an apocalyptic number.

It is an amenable number.

21100021021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21100021021 is an equidigital number, since it uses as much as digits as its factorization.

21100021021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21100021021 its reverse (12012000112), we get a palindrome (33112021133).

The spelling of 21100021021 in words is "twenty-one billion, one hundred million, twenty-one thousand, twenty-one".