21210111012221 has 2 divisors, whose sum is σ = 21210111012222. Its totient is φ = 21210111012220.

The previous prime is 21210111012173. The next prime is 21210111012347. The reversal of 21210111012221 is 12221011101212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20943711544900 + 266399467321 = 4576430^2 + 516139^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210111012221 - 2¹⁴ = 21210110995837 is a prime.

It is a super-2 number, since 2×21210111012221² (a number of 27 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21210111012221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210111012521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605055506110 + 10605055506111.

It is an arithmetic number, because the mean of its divisors is an integer number (10605055506111).

Almost surely, 2^{21210111012221} is an apocalyptic number.

It is an amenable number.

21210111012221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210111012221 is an equidigital number, since it uses as much as digits as its factorization.

21210111012221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 17.

Adding to 21210111012221 its reverse (12221011101212), we get a palindrome (33431122113433).

The spelling of 21210111012221 in words is "twenty-one trillion, two hundred ten billion, one hundred eleven million, twelve thousand, two hundred twenty-one".