21103312081 has 2 divisors, whose sum is σ = 21103312082. Its totient is φ = 21103312080.

The previous prime is 21103312063. The next prime is 21103312123. The reversal of 21103312081 is 18021330112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14324259856 + 6779052225 = 119684^2 + 82335^2 .

It is a cyclic number.

It is not a de Polignac number, because 21103312081 - 2⁹ = 21103311569 is a prime.

It is a super-2 number, since 2×21103312081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21103312051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551656040 + 10551656041.

It is an arithmetic number, because the mean of its divisors is an integer number (10551656041).

Almost surely, 2^21103312081 is an apocalyptic number.

It is an amenable number.

21103312081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21103312081 is an equidigital number, since it uses as much as digits as its factorization.

21103312081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 22.

Adding to 21103312081 its reverse (18021330112), we get a palindrome (39124642193).

The spelling of 21103312081 in words is "twenty-one billion, one hundred three million, three hundred twelve thousand, eighty-one".