21110211111221 has 4 divisors (see below), whose sum is σ = 21110231663532. Its totient is φ = 21110190558912.

The previous prime is 21110211111173. The next prime is 21110211111233. The reversal of 21110211111221 is 12211111201112.

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 21083433388900 + 26777722321 = 4591670^2 + 163639^2 .

It is a cyclic number.

It is not a de Polignac number, because 21110211111221 - 2³⁴ = 21093031242037 is a prime.

It is a super-2 number, since 2×21110211111221² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21110211111221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21110211711221) 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, 8649620 + ... + 10818333.

It is an arithmetic number, because the mean of its divisors is an integer number (5277557915883).

Almost surely, 2^{21110211111221} is an apocalyptic number.

It is an amenable number.

21110211111221 is a deficient number, since it is larger than the sum of its proper divisors (20552311).

21110211111221 is a wasteful number, since it uses less digits than its factorization.

21110211111221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20552310.

The product of its (nonzero) digits is 16, while the sum is 17.

Adding to 21110211111221 its reverse (12211111201112), we get a palindrome (33321322312333).

The spelling of 21110211111221 in words is "twenty-one trillion, one hundred ten billion, two hundred eleven million, one hundred eleven thousand, two hundred twenty-one".