21013123021 has 16 divisors (see below), whose sum is σ = 24014073600. Its totient is φ = 18210628800.

The previous prime is 21013122983. The next prime is 21013123051. The reversal of 21013123021 is 12032131012.

It is a cyclic number.

It is not a de Polignac number, because 21013123021 - 2²⁹ = 20476252109 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21013122986 and 21013123004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013123051) 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, 391710 + ... + 442111.

It is an arithmetic number, because the mean of its divisors is an integer number (1500879600).

Almost surely, 2^21013123021 is an apocalyptic number.

It is an amenable number.

21013123021 is a deficient number, since it is larger than the sum of its proper divisors (3000950579).

21013123021 is a wasteful number, since it uses less digits than its factorization.

21013123021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 833940.

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 21013123021 its reverse (12032131012), we get a palindrome (33045254033).

The spelling of 21013123021 in words is "twenty-one billion, thirteen million, one hundred twenty-three thousand, twenty-one".