21000012200021 has 4 divisors (see below), whose sum is σ = 21002317622700. Its totient is φ = 20997706777344.

The previous prime is 21000012199987. The next prime is 21000012200053. The reversal of 21000012200021 is 12000221000012.

It is a happy number.

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 2236266022225 + 18763746177796 = 1495415^2 + 4331714^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000012200021 - 2³⁸ = 20725134293077 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21000012199975 and 21000012200011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000012200221) 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, 1152697676 + ... + 1152715893.

It is an arithmetic number, because the mean of its divisors is an integer number (5250579405675).

Almost surely, 2^{21000012200021} is an apocalyptic number.

It is an amenable number.

21000012200021 is a deficient number, since it is larger than the sum of its proper divisors (2305422679).

21000012200021 is an equidigital number, since it uses as much as digits as its factorization.

21000012200021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2305422678.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21000012200021 its reverse (12000221000012), we get a palindrome (33000233200033).

The spelling of 21000012200021 in words is "twenty-one trillion, twelve million, two hundred thousand, twenty-one".