21204103021 has 2 divisors, whose sum is σ = 21204103022. Its totient is φ = 21204103020.

The previous prime is 21204102991. The next prime is 21204103027. The reversal of 21204103021 is 12030140212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20082857796 + 1121245225 = 141714^2 + 33485^2 .

It is a cyclic number.

It is not a de Polignac number, because 21204103021 - 2⁵ = 21204102989 is a prime.

It is a super-2 number, since 2×21204103021² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21204102986 and 21204103004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21204103027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602051510 + 10602051511.

It is an arithmetic number, because the mean of its divisors is an integer number (10602051511).

Almost surely, 2^21204103021 is an apocalyptic number.

It is an amenable number.

21204103021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21204103021 is an equidigital number, since it uses as much as digits as its factorization.

21204103021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 16.

Adding to 21204103021 its reverse (12030140212), we get a palindrome (33234243233).

The spelling of 21204103021 in words is "twenty-one billion, two hundred four million, one hundred three thousand, twenty-one".