21201121211221 has 16 divisors (see below), whose sum is σ = 24339034137600. Its totient is φ = 18090507149568.

The previous prime is 21201121211147. The next prime is 21201121211279. The reversal of 21201121211221 is 12211212110212.

It is a happy number.

It is not a de Polignac number, because 21201121211221 - 2⁷ = 21201121211093 is a prime.

It is a super-2 number, since 2×21201121211221² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201121211821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 89372115 + ... + 89609023.

It is an arithmetic number, because the mean of its divisors is an integer number (1521189633600).

Almost surely, 2^{21201121211221} is an apocalyptic number.

It is an amenable number.

21201121211221 is a deficient number, since it is larger than the sum of its proper divisors (3137912926379).

21201121211221 is a wasteful number, since it uses less digits than its factorization.

21201121211221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 294468.

The product of its (nonzero) digits is 64, while the sum is 19.

Adding to 21201121211221 its reverse (12211212110212), we get a palindrome (33412333321433).

It can be divided in two parts, 2120112 and 1211221, that added together give a palindrome (3331333).

The spelling of 21201121211221 in words is "twenty-one trillion, two hundred one billion, one hundred twenty-one million, two hundred eleven thousand, two hundred twenty-one".