21111212122081 has 2 divisors, whose sum is σ = 21111212122082. Its totient is φ = 21111212122080.

The previous prime is 21111212122027. The next prime is 21111212122151. The reversal of 21111212122081 is 18022121211112.

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., 20255940435600 + 855271686481 = 4500660^2 + 924809^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111212122081 - 2³⁹ = 20561456308193 is a prime.

It is a super-2 number, since 2×21111212122081² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21111212132081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555606061040 + 10555606061041.

It is an arithmetic number, because the mean of its divisors is an integer number (10555606061041).

Almost surely, 2^{21111212122081} is an apocalyptic number.

It is an amenable number.

21111212122081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111212122081 is an equidigital number, since it uses as much as digits as its factorization.

21111212122081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 25.

Adding to 21111212122081 its reverse (18022121211112), we get a palindrome (39133333333193).

The spelling of 21111212122081 in words is "twenty-one trillion, one hundred eleven billion, two hundred twelve million, one hundred twenty-two thousand, eighty-one".