21120010000021 has 4 divisors (see below), whose sum is σ = 22362363529452. Its totient is φ = 19877656470592.

The previous prime is 21120010000009. The next prime is 21120010000049. The reversal of 21120010000021 is 12000001002112.

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 13666618591921 + 7453391408100 = 3696839^2 + 2730090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120010000021 - 2⁹ = 21120009999509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21120009999962 and 21120010000007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120010000121) 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, 621176764690 + ... + 621176764723.

It is an arithmetic number, because the mean of its divisors is an integer number (5590590882363).

Almost surely, 2^{21120010000021} is an apocalyptic number.

It is an amenable number.

21120010000021 is a deficient number, since it is larger than the sum of its proper divisors (1242353529431).

21120010000021 is a wasteful number, since it uses less digits than its factorization.

21120010000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1242353529430.

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21120010000021 its reverse (12000001002112), we get a palindrome (33120011002133).

The spelling of 21120010000021 in words is "twenty-one trillion, one hundred twenty billion, ten million, twenty-one", and thus it is an aban number.