21666844794239 has 2 divisors, whose sum is σ = 21666844794240. Its totient is φ = 21666844794238.

The previous prime is 21666844794193. The next prime is 21666844794263. The reversal of 21666844794239 is 93249744866612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21666844794239 - 2²⁸ = 21666576358783 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21666844794139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10833422397119 + 10833422397120.

It is an arithmetic number, because the mean of its divisors is an integer number (10833422397120).

Almost surely, 2^{21666844794239} is an apocalyptic number.

21666844794239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666844794239 is an equidigital number, since it uses as much as digits as its factorization.

21666844794239 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 752467968, while the sum is 71.

The spelling of 21666844794239 in words is "twenty-one trillion, six hundred sixty-six billion, eight hundred forty-four million, seven hundred ninety-four thousand, two hundred thirty-nine".