21011323121 has 2 divisors, whose sum is σ = 21011323122. Its totient is φ = 21011323120.

The previous prime is 21011323117. The next prime is 21011323129. The reversal of 21011323121 is 12132311012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20025363121 + 985960000 = 141511^2 + 31400^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011323121 - 2² = 21011323117 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21011323121.

It is not a weakly prime, because it can be changed into another prime (21011323129) 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, 10505661560 + 10505661561.

It is an arithmetic number, because the mean of its divisors is an integer number (10505661561).

Almost surely, 2^21011323121 is an apocalyptic number.

It is an amenable number.

21011323121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011323121 is an equidigital number, since it uses as much as digits as its factorization.

21011323121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 17.

Adding to 21011323121 its reverse (12132311012), we get a palindrome (33143634133).

The spelling of 21011323121 in words is "twenty-one billion, eleven million, three hundred twenty-three thousand, one hundred twenty-one".