21212111201221 has 2 divisors, whose sum is σ = 21212111201222. Its totient is φ = 21212111201220.

The previous prime is 21212111201207. The next prime is 21212111201279. The reversal of 21212111201221 is 12210211121212.

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., 18745999012225 + 2466112188996 = 4329665^2 + 1570386^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212111201221 - 2⁷ = 21212111201093 is a prime.

It is a super-2 number, since 2×21212111201221² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21212111201201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606055600610 + 10606055600611.

It is an arithmetic number, because the mean of its divisors is an integer number (10606055600611).

Almost surely, 2^{21212111201221} is an apocalyptic number.

It is an amenable number.

21212111201221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212111201221 is an equidigital number, since it uses as much as digits as its factorization.

21212111201221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64, while the sum is 19.

Adding to 21212111201221 its reverse (12210211121212), we get a palindrome (33422322322433).

The spelling of 21212111201221 in words is "twenty-one trillion, two hundred twelve billion, one hundred eleven million, two hundred one thousand, two hundred twenty-one".