21221110122221 has 2 divisors, whose sum is σ = 21221110122222. Its totient is φ = 21221110122220.

The previous prime is 21221110122197. The next prime is 21221110122323. The reversal of 21221110122221 is 12222101112212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16297974555625 + 4923135566596 = 4037075^2 + 2218814^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221110122221 - 2¹⁸ = 21221109860077 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21221110122193 and 21221110122202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221113122221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610555061110 + 10610555061111.

It is an arithmetic number, because the mean of its divisors is an integer number (10610555061111).

Almost surely, 2^{21221110122221} is an apocalyptic number.

It is an amenable number.

21221110122221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221110122221 is an equidigital number, since it uses as much as digits as its factorization.

21221110122221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 20.

Adding to 21221110122221 its reverse (12222101112212), we get a palindrome (33443211234433).

The spelling of 21221110122221 in words is "twenty-one trillion, two hundred twenty-one billion, one hundred ten million, one hundred twenty-two thousand, two hundred twenty-one".