21220001221 has 2 divisors, whose sum is σ = 21220001222. Its totient is φ = 21220001220.

The previous prime is 21220001219. The next prime is 21220001267. The reversal of 21220001221 is 12210002212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16637388196 + 4582613025 = 128986^2 + 67695^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220001221 - 2¹ = 21220001219 is a prime.

Together with 21220001219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21220001281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610000610 + 10610000611.

It is an arithmetic number, because the mean of its divisors is an integer number (10610000611).

Almost surely, 2^21220001221 is an apocalyptic number.

It is an amenable number.

21220001221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220001221 is an equidigital number, since it uses as much as digits as its factorization.

21220001221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21220001221 its reverse (12210002212), we get a palindrome (33430003433).

Subtracting from 21220001221 its reverse (12210002212), we obtain a palindrome (9009999009).

The spelling of 21220001221 in words is "twenty-one billion, two hundred twenty million, one thousand, two hundred twenty-one".