21338809021 has 2 divisors, whose sum is σ = 21338809022. Its totient is φ = 21338809020.

The previous prime is 21338808991. The next prime is 21338809043. The reversal of 21338809021 is 12090883312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11575392921 + 9763416100 = 107589^2 + 98810^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21338809021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21338809081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10669404510 + 10669404511.

It is an arithmetic number, because the mean of its divisors is an integer number (10669404511).

Almost surely, 2^21338809021 is an apocalyptic number.

It is an amenable number.

21338809021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21338809021 is an equidigital number, since it uses as much as digits as its factorization.

21338809021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 37.

The spelling of 21338809021 in words is "twenty-one billion, three hundred thirty-eight million, eight hundred nine thousand, twenty-one".