21021200121221 has 4 divisors (see below), whose sum is σ = 21257393381100. Its totient is φ = 20785006861344.

The previous prime is 21021200121211. The next prime is 21021200121223. The reversal of 21021200121221 is 12212100212012.

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 10955365192321 + 10065834928900 = 3309889^2 + 3172670^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021200121221 - 2¹⁴ = 21021200104837 is a prime.

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 21021200121221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021200121223) 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, 118096629806 + ... + 118096629983.

It is an arithmetic number, because the mean of its divisors is an integer number (5314348345275).

Almost surely, 2^{21021200121221} is an apocalyptic number.

It is an amenable number.

21021200121221 is a deficient number, since it is larger than the sum of its proper divisors (236193259879).

21021200121221 is an equidigital number, since it uses as much as digits as its factorization.

21021200121221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236193259878.

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

Adding to 21021200121221 its reverse (12212100212012), we get a palindrome (33233300333233).

The spelling of 21021200121221 in words is "twenty-one trillion, twenty-one billion, two hundred million, one hundred twenty-one thousand, two hundred twenty-one".