21201012121 has 2 divisors, whose sum is σ = 21201012122. Its totient is φ = 21201012120.

The previous prime is 21201012043. The next prime is 21201012163. The reversal of 21201012121 is 12121010212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13768675600 + 7432336521 = 117340^2 + 86211^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201012121 - 2⁹ = 21201011609 is a prime.

It is not a weakly prime, because it can be changed into another prime (21201012181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600506060 + 10600506061.

It is an arithmetic number, because the mean of its divisors is an integer number (10600506061).

Almost surely, 2^21201012121 is an apocalyptic number.

It is an amenable number.

21201012121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201012121 is an equidigital number, since it uses as much as digits as its factorization.

21201012121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21201012121 its reverse (12121010212), we get a palindrome (33322022333).

The spelling of 21201012121 in words is "twenty-one billion, two hundred one million, twelve thousand, one hundred twenty-one".