21115664461 has 2 divisors, whose sum is σ = 21115664462. Its totient is φ = 21115664460.

The previous prime is 21115664407. The next prime is 21115664483. The reversal of 21115664461 is 16446651112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20900484900 + 215179561 = 144570^2 + 14669^2 .

It is a cyclic number.

It is not a de Polignac number, because 21115664461 - 2⁹ = 21115663949 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21115664461.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21115364461) 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, 10557832230 + 10557832231.

It is an arithmetic number, because the mean of its divisors is an integer number (10557832231).

Almost surely, 2^21115664461 is an apocalyptic number.

It is an amenable number.

21115664461 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115664461 is an equidigital number, since it uses as much as digits as its factorization.

21115664461 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34560, while the sum is 37.

The spelling of 21115664461 in words is "twenty-one billion, one hundred fifteen million, six hundred sixty-four thousand, four hundred sixty-one".