21430321021 has 2 divisors, whose sum is σ = 21430321022. Its totient is φ = 21430321020.

The previous prime is 21430321013. The next prime is 21430321039. The reversal of 21430321021 is 12012303412.

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., 16913002500 + 4517318521 = 130050^2 + 67211^2 .

It is a cyclic number.

It is not a de Polignac number, because 21430321021 - 2³ = 21430321013 is a prime.

It is a super-2 number, since 2×21430321021² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21430321021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21430321061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715160510 + 10715160511.

It is an arithmetic number, because the mean of its divisors is an integer number (10715160511).

Almost surely, 2^21430321021 is an apocalyptic number.

It is an amenable number.

21430321021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21430321021 is an equidigital number, since it uses as much as digits as its factorization.

21430321021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21430321021 its reverse (12012303412), we get a palindrome (33442624433).

The spelling of 21430321021 in words is "twenty-one billion, four hundred thirty million, three hundred twenty-one thousand, twenty-one".