21211312221 has 36 divisors (see below), whose sum is σ = 33736462396. Its totient is φ = 12832680960.

The previous prime is 21211312189. The next prime is 21211312259. The reversal of 21211312221 is 12221311212.

It can be written as a sum of positive squares in 2 ways, for example, as 18458211321 + 2753100900 = 135861^2 + 52470^2 .

It is not a de Polignac number, because 21211312221 - 2⁵ = 21211312189 is a prime.

It is a super-2 number, since 2×21211312221² (a number of 21 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 = 21211312194 and 21211312203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211312261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 611475 + ... + 645231.

Almost surely, 2^21211312221 is an apocalyptic number.

It is an amenable number.

21211312221 is a deficient number, since it is larger than the sum of its proper divisors (12525150175).

21211312221 is a wasteful number, since it uses less digits than its factorization.

21211312221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34362 (or 34348 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

Adding to 21211312221 its reverse (12221311212), we get a palindrome (33432623433).

The spelling of 21211312221 in words is "twenty-one billion, two hundred eleven million, three hundred twelve thousand, two hundred twenty-one".