21200121201221 has 16 divisors (see below), whose sum is σ = 22973766222528. Its totient is φ = 19485168864000.

The previous prime is 21200121201157. The next prime is 21200121201223. The reversal of 21200121201221 is 12210212100212.

It is a cyclic number.

It is not a de Polignac number, because 21200121201221 - 2⁶ = 21200121201157 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

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 21200121201221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21200121201223) 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, 821411 + ... + 6563151.

It is an arithmetic number, because the mean of its divisors is an integer number (1435860388908).

Almost surely, 2^{21200121201221} is an apocalyptic number.

It is an amenable number.

21200121201221 is a deficient number, since it is larger than the sum of its proper divisors (1773645021307).

21200121201221 is a wasteful number, since it uses less digits than its factorization.

21200121201221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5746852.

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 21200121201221 its reverse (12210212100212), we get a palindrome (33410333301433).

It can be divided in two parts, 2120012 and 1201221, that added together give a palindrome (3321233).

The spelling of 21200121201221 in words is "twenty-one trillion, two hundred billion, one hundred twenty-one million, two hundred one thousand, two hundred twenty-one".