21211120121 has 2 divisors, whose sum is σ = 21211120122. Its totient is φ = 21211120120.

The previous prime is 21211120081. The next prime is 21211120123. The reversal of 21211120121 is 12102111212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19337961721 + 1873158400 = 139061^2 + 43280^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211120121 - 2¹⁸ = 21210857977 is a prime.

It is a Sophie Germain prime.

Together with 21211120123, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21211120096 and 21211120105.

It is not a weakly prime, because it can be changed into another prime (21211120123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605560060 + 10605560061.

It is an arithmetic number, because the mean of its divisors is an integer number (10605560061).

Almost surely, 2^21211120121 is an apocalyptic number.

It is an amenable number.

21211120121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211120121 is an equidigital number, since it uses as much as digits as its factorization.

21211120121 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 14.

Adding to 21211120121 its reverse (12102111212), we get a palindrome (33313231333).

It can be divided in two parts, 212111 and 20121, that added together give a palindrome (232232).

The spelling of 21211120121 in words is "twenty-one billion, two hundred eleven million, one hundred twenty thousand, one hundred twenty-one".