21011030021 has 16 divisors (see below), whose sum is σ = 21625240320. Its totient is φ = 20406988800.

The previous prime is 21011030003. The next prime is 21011030041. The reversal of 21011030021 is 12003011012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011030021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21011029984 and 21011030011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011030041) 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, 2183621 + ... + 2193221.

It is an arithmetic number, because the mean of its divisors is an integer number (1351577520).

Almost surely, 2^21011030021 is an apocalyptic number.

It is an amenable number.

21011030021 is a deficient number, since it is larger than the sum of its proper divisors (614210299).

21011030021 is an equidigital number, since it uses as much as digits as its factorization.

21011030021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10124.

The product of its (nonzero) digits is 12, while the sum is 11.

Adding to 21011030021 its reverse (12003011012), we get a palindrome (33014041033).

The spelling of 21011030021 in words is "twenty-one billion, eleven million, thirty thousand, twenty-one".