21043043021 has 16 divisors (see below), whose sum is σ = 28253597568. Its totient is φ = 15135854400.

The previous prime is 21043043011. The next prime is 21043043027. The reversal of 21043043021 is 12034034012.

It is a cyclic number.

It is not a de Polignac number, because 21043043021 - 2²⁶ = 20975934157 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21043042984 and 21043043002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21043043027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10510010 + ... + 10512011.

It is an arithmetic number, because the mean of its divisors is an integer number (1765849848).

Almost surely, 2^21043043021 is an apocalyptic number.

It is an amenable number.

21043043021 is a deficient number, since it is larger than the sum of its proper divisors (7210554547).

21043043021 is a wasteful number, since it uses less digits than its factorization.

21043043021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21022052.

The product of its (nonzero) digits is 576, while the sum is 20.

Adding to 21043043021 its reverse (12034034012), we get a palindrome (33077077033).

Subtracting from 21043043021 its reverse (12034034012), we obtain a palindrome (9009009009).

The spelling of 21043043021 in words is "twenty-one billion, forty-three million, forty-three thousand, twenty-one".