21200121122221 has 4 divisors (see below), whose sum is σ = 21201130048252. Its totient is φ = 21199112196192.

The previous prime is 21200121122209. The next prime is 21200121122269. The reversal of 21200121122221 is 12222112100212.

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 3811104362025 + 17389016760196 = 1952205^2 + 4170014^2 .

It is a cyclic number.

It is not a de Polignac number, because 21200121122221 - 2¹¹ = 21200121120173 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 (21200121126221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 504431496 + ... + 504473521.

It is an arithmetic number, because the mean of its divisors is an integer number (5300282512063).

Almost surely, 2^{21200121122221} is an apocalyptic number.

It is an amenable number.

21200121122221 is a deficient number, since it is larger than the sum of its proper divisors (1008926031).

21200121122221 is a wasteful number, since it uses less digits than its factorization.

21200121122221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1008926030.

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

Adding to 21200121122221 its reverse (12222112100212), we get a palindrome (33422233222433).

The spelling of 21200121122221 in words is "twenty-one trillion, two hundred billion, one hundred twenty-one million, one hundred twenty-two thousand, two hundred twenty-one".