21011210211221 has 2 divisors, whose sum is σ = 21011210211222. Its totient is φ = 21011210211220.

The previous prime is 21011210211191. The next prime is 21011210211223. The reversal of 21011210211221 is 12211201211012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19451284150321 + 1559926060900 = 4410361^2 + 1248970^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011210211221 - 2⁶ = 21011210211157 is a prime.

Together with 21011210211223, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21011210211221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011210211223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505605105610 + 10505605105611.

It is an arithmetic number, because the mean of its divisors is an integer number (10505605105611).

Almost surely, 2^{21011210211221} is an apocalyptic number.

It is an amenable number.

21011210211221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011210211221 is an equidigital number, since it uses as much as digits as its factorization.

21011210211221 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 17.

Adding to 21011210211221 its reverse (12211201211012), we get a palindrome (33222411422233).

The spelling of 21011210211221 in words is "twenty-one trillion, eleven billion, two hundred ten million, two hundred eleven thousand, two hundred twenty-one".