221212121021 has 2 divisors, whose sum is σ = 221212121022. Its totient is φ = 221212121020.

The previous prime is 221212120999. The next prime is 221212121023. The reversal of 221212121021 is 120121212122.

221212121021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 128799160996 + 92412960025 = 358886^2 + 303995^2 .

It is a cyclic number.

It is not a de Polignac number, because 221212121021 - 2¹⁴ = 221212104637 is a prime.

Together with 221212121023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221212121023) 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 as a sum of consecutive naturals, namely, 110606060510 + 110606060511.

It is an arithmetic number, because the mean of its divisors is an integer number (110606060511).

Almost surely, 2^221212121021 is an apocalyptic number.

It is an amenable number.

221212121021 is a deficient number, since it is larger than the sum of its proper divisors (1).

221212121021 is an equidigital number, since it uses as much as digits as its factorization.

221212121021 is an odious number, because the sum of its binary digits is odd.

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

Adding to 221212121021 its reverse (120121212122), we get a palindrome (341333333143).

The spelling of 221212121021 in words is "two hundred twenty-one billion, two hundred twelve million, one hundred twenty-one thousand, twenty-one".