21220121201221 has 8 divisors (see below), whose sum is σ = 21236538141720. Its totient is φ = 21203710564608.

The previous prime is 21220121201179. The next prime is 21220121201243. The reversal of 21220121201221 is 12210212102212.

It can be written as a sum of positive squares in 4 ways, for example, as 47598148900 + 21172523052321 = 218170^2 + 4601361^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21220121201221 - 2⁹ = 21220121200709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220121204221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5170185 + ... + 8316913.

It is an arithmetic number, because the mean of its divisors is an integer number (2654567267715).

Almost surely, 2^{21220121201221} is an apocalyptic number.

It is an amenable number.

21220121201221 is a deficient number, since it is larger than the sum of its proper divisors (16416940499).

21220121201221 is a wasteful number, since it uses less digits than its factorization.

21220121201221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3151943.

The product of its (nonzero) digits is 128, while the sum is 19.

Adding to 21220121201221 its reverse (12210212102212), we get a palindrome (33430333303433).

Subtracting from 21220121201221 its reverse (12210212102212), we obtain a palindrome (9009909099009).

It can be divided in two parts, 2122012 and 1201221, that added together give a palindrome (3323233).

The spelling of 21220121201221 in words is "twenty-one trillion, two hundred twenty billion, one hundred twenty-one million, two hundred one thousand, two hundred twenty-one".