21304030021 has 2 divisors, whose sum is σ = 21304030022. Its totient is φ = 21304030020.

The previous prime is 21304030001. The next prime is 21304030061. The reversal of 21304030021 is 12003040312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17958680100 + 3345349921 = 134010^2 + 57839^2 .

It is a cyclic number.

It is not a de Polignac number, because 21304030021 - 2¹⁷ = 21303898949 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21304029977 and 21304030004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21304030001) 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, 10652015010 + 10652015011.

It is an arithmetic number, because the mean of its divisors is an integer number (10652015011).

Almost surely, 2^21304030021 is an apocalyptic number.

It is an amenable number.

21304030021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21304030021 is an equidigital number, since it uses as much as digits as its factorization.

21304030021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 16.

Adding to 21304030021 its reverse (12003040312), we get a palindrome (33307070333).

The spelling of 21304030021 in words is "twenty-one billion, three hundred four million, thirty thousand, twenty-one".