21210222100021 has 4 divisors (see below), whose sum is σ = 21212449840044. Its totient is φ = 21207994360000.

The previous prime is 21210222100013. The next prime is 21210222100033. The reversal of 21210222100021 is 12000122201212.

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 8845954866225 + 12364267233796 = 2974215^2 + 3516286^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210222100021 - 2³ = 21210222100013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210222099968 and 21210222100004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210222100051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1113855730 + ... + 1113874771.

It is an arithmetic number, because the mean of its divisors is an integer number (5303112460011).

Almost surely, 2^{21210222100021} is an apocalyptic number.

It is an amenable number.

21210222100021 is a deficient number, since it is larger than the sum of its proper divisors (2227740023).

21210222100021 is an equidigital number, since it uses as much as digits as its factorization.

21210222100021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2227740022.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21210222100021 its reverse (12000122201212), we get a palindrome (33210344301233).

The spelling of 21210222100021 in words is "twenty-one trillion, two hundred ten billion, two hundred twenty-two million, one hundred thousand, twenty-one".