21000020013 has 24 divisors (see below), whose sum is σ = 36190512960. Its totient is φ = 12000010680.

The previous prime is 21000019991. The next prime is 21000020053. The reversal of 21000020013 is 31002000012.

It is a happy number.

It is not a de Polignac number, because 21000020013 - 2⁹ = 21000019501 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21000019977 and 21000020004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000020053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7935193 + ... + 7937838.

It is an arithmetic number, because the mean of its divisors is an integer number (1507938040).

Almost surely, 2^21000020013 is an apocalyptic number.

It is an amenable number.

21000020013 is a deficient number, since it is larger than the sum of its proper divisors (15190492947).

21000020013 is a wasteful number, since it uses less digits than its factorization.

21000020013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15873054 (or 15873041 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

Adding to 21000020013 its reverse (31002000012), we get a palindrome (52002020025).

The spelling of 21000020013 in words is "twenty-one billion, twenty thousand, thirteen".