21210020021021 has 4 divisors (see below), whose sum is σ = 22841560022652. Its totient is φ = 19578480019392.

The previous prime is 21210020020907. The next prime is 21210020021023. The reversal of 21210020021021 is 12012002001212.

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 6173540284921 + 15036479736100 = 2484661^2 + 3877690^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210020021021 - 2³⁴ = 21192840151837 is a prime.

It is a super-2 number, since 2×21210020021021² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210020020987 and 21210020021005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210020021023) 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, 815770000796 + ... + 815770000821.

It is an arithmetic number, because the mean of its divisors is an integer number (5710390005663).

Almost surely, 2^{21210020021021} is an apocalyptic number.

It is an amenable number.

21210020021021 is a deficient number, since it is larger than the sum of its proper divisors (1631540001631).

21210020021021 is a wasteful number, since it uses less digits than its factorization.

21210020021021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1631540001630.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21210020021021 its reverse (12012002001212), we get a palindrome (33222022022233).

The spelling of 21210020021021 in words is "twenty-one trillion, two hundred ten billion, twenty million, twenty-one thousand, twenty-one".