21013213021 has 4 divisors (see below), whose sum is σ = 21060013500. Its totient is φ = 20966412544.

The previous prime is 21013213019. The next prime is 21013213043. The reversal of 21013213021 is 12031231012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10132636921 + 10880576100 = 100661^2 + 104310^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013213021 - 2¹ = 21013213019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21013212986 and 21013213004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013217021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23399566 + ... + 23400463.

It is an arithmetic number, because the mean of its divisors is an integer number (5265003375).

Almost surely, 2^21013213021 is an apocalyptic number.

It is an amenable number.

21013213021 is a deficient number, since it is larger than the sum of its proper divisors (46800479).

21013213021 is an equidigital number, since it uses as much as digits as its factorization.

21013213021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46800478.

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

Adding to 21013213021 its reverse (12031231012), we get a palindrome (33044444033).

The spelling of 21013213021 in words is "twenty-one billion, thirteen million, two hundred thirteen thousand, twenty-one".