21210202021221 has 20 divisors (see below), whose sum is σ = 31975058219500. Its totient is φ = 14010408668736.

The previous prime is 21210202021201. The next prime is 21210202021237. The reversal of 21210202021221 is 12212020201212.

It is a happy number.

21210202021221 is a `hidden beast` number, since 21 + 210 + 202 + 0 + 212 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 11325654660321 + 9884547360900 = 3365361^2 + 3143970^2 .

It is not a de Polignac number, because 21210202021221 - 2¹⁰ = 21210202020197 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210202021194 and 21210202021203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210202021201) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1201157896 + ... + 1201175553.

It is an arithmetic number, because the mean of its divisors is an integer number (1598752910975).

Almost surely, 2^{21210202021221} is an apocalyptic number.

It is an amenable number.

21210202021221 is a deficient number, since it is larger than the sum of its proper divisors (10764856198279).

21210202021221 is a wasteful number, since it uses less digits than its factorization.

21210202021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2402333570 (or 2402333561 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

Adding to 21210202021221 its reverse (12212020201212), we get a palindrome (33422222222433).

The spelling of 21210202021221 in words is "twenty-one trillion, two hundred ten billion, two hundred two million, twenty-one thousand, two hundred twenty-one".