21201220221221 has 2 divisors, whose sum is σ = 21201220221222. Its totient is φ = 21201220221220.

The previous prime is 21201220221191. The next prime is 21201220221229. The reversal of 21201220221221 is 12212202210212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15679707177121 + 5521513044100 = 3959761^2 + 2349790^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201220221221 - 2²⁶ = 21201153112357 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21201220221193 and 21201220221202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201220221229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600610110610 + 10600610110611.

It is an arithmetic number, because the mean of its divisors is an integer number (10600610110611).

Almost surely, 2^{21201220221221} is an apocalyptic number.

It is an amenable number.

21201220221221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201220221221 is an equidigital number, since it uses as much as digits as its factorization.

21201220221221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 20.

Adding to 21201220221221 its reverse (12212202210212), we get a palindrome (33413422431433).

The spelling of 21201220221221 in words is "twenty-one trillion, two hundred one billion, two hundred twenty million, two hundred twenty-one thousand, two hundred twenty-one".