21115666506013 has 2 divisors, whose sum is σ = 21115666506014. Its totient is φ = 21115666506012.

The previous prime is 21115666506007. The next prime is 21115666506023. The reversal of 21115666506013 is 31060566651112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17799851306169 + 3315815199844 = 4218987^2 + 1820938^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21115666506013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21115666506023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557833253006 + 10557833253007.

It is an arithmetic number, because the mean of its divisors is an integer number (10557833253007).

Almost surely, 2^{21115666506013} is an apocalyptic number.

It is an amenable number.

21115666506013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115666506013 is an equidigital number, since it uses as much as digits as its factorization.

21115666506013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 194400, while the sum is 43.

The spelling of 21115666506013 in words is "twenty-one trillion, one hundred fifteen billion, six hundred sixty-six million, five hundred six thousand, thirteen".