21212221101221 has 2 divisors, whose sum is σ = 21212221101222. Its totient is φ = 21212221101220.

The previous prime is 21212221101209. The next prime is 21212221101271. The reversal of 21212221101221 is 12210112221212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21164701461121 + 47519640100 = 4600511^2 + 217990^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212221101221 - 2¹⁰ = 21212221100197 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21212221101193 and 21212221101202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21212221101271) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606110550610 + 10606110550611.

It is an arithmetic number, because the mean of its divisors is an integer number (10606110550611).

Almost surely, 2^{21212221101221} is an apocalyptic number.

It is an amenable number.

21212221101221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212221101221 is an equidigital number, since it uses as much as digits as its factorization.

21212221101221 is an evil number, because the sum of its binary digits is even.

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

Adding to 21212221101221 its reverse (12210112221212), we get a palindrome (33422333322433).

The spelling of 21212221101221 in words is "twenty-one trillion, two hundred twelve billion, two hundred twenty-one million, one hundred one thousand, two hundred twenty-one".