21011212121 has 2 divisors, whose sum is σ = 21011212122. Its totient is φ = 21011212120.

The previous prime is 21011212093. The next prime is 21011212139. The reversal of 21011212121 is 12121211012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19583203600 + 1428008521 = 139940^2 + 37789^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011212121 - 2²² = 21007017817 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21011212096 and 21011212105.

It is not a weakly prime, because it can be changed into another prime (21011212141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505606060 + 10505606061.

It is an arithmetic number, because the mean of its divisors is an integer number (10505606061).

Almost surely, 2^21011212121 is an apocalyptic number.

It is an amenable number.

21011212121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011212121 is an equidigital number, since it uses as much as digits as its factorization.

21011212121 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 14.

Adding to 21011212121 its reverse (12121211012), we get a palindrome (33132423133).

The spelling of 21011212121 in words is "twenty-one billion, eleven million, two hundred twelve thousand, one hundred twenty-one".