21003430021 has 12 divisors (see below), whose sum is σ = 25028479980. Its totient is φ = 17563842240.

The previous prime is 21003429971. The next prime is 21003430039. The reversal of 21003430021 is 12003430012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 8670216996 + 12333213025 = 93114^2 + 111055^2 .

It is not a de Polignac number, because 21003430021 - 2¹⁹ = 21002905733 is a prime.

It is a super-2 number, since 2×21003430021² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21003429977 and 21003430004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003430051) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5225326 + ... + 5229343.

It is an arithmetic number, because the mean of its divisors is an integer number (2085706665).

Almost surely, 2^21003430021 is an apocalyptic number.

It is an amenable number.

21003430021 is a deficient number, since it is larger than the sum of its proper divisors (4025049959).

21003430021 is a wasteful number, since it uses less digits than its factorization.

21003430021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10454724 (or 10454717 counting only the distinct ones).

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

Adding to 21003430021 its reverse (12003430012), we get a palindrome (33006860033).

Subtracting from 21003430021 its reverse (12003430012), we obtain a palindrome (9000000009).

The spelling of 21003430021 in words is "twenty-one billion, three million, four hundred thirty thousand, twenty-one".