21210111112121 has 2 divisors, whose sum is σ = 21210111112122. Its totient is φ = 21210111112120.

The previous prime is 21210111112067. The next prime is 21210111112129. The reversal of 21210111112121 is 12121111101212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19847568513721 + 1362542598400 = 4455061^2 + 1167280^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210111112121 - 2²² = 21210106917817 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21210111112121.

It is not a weakly prime, because it can be changed into another prime (21210111112129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605055556060 + 10605055556061.

It is an arithmetic number, because the mean of its divisors is an integer number (10605055556061).

Almost surely, 2^{21210111112121} is an apocalyptic number.

It is an amenable number.

21210111112121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210111112121 is an equidigital number, since it uses as much as digits as its factorization.

21210111112121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 17.

Adding to 21210111112121 its reverse (12121111101212), we get a palindrome (33331222213333).

The spelling of 21210111112121 in words is "twenty-one trillion, two hundred ten billion, one hundred eleven million, one hundred twelve thousand, one hundred twenty-one".