21666844794263 has 2 divisors, whose sum is σ = 21666844794264. Its totient is φ = 21666844794262.

The previous prime is 21666844794239. The next prime is 21666844794307. The reversal of 21666844794263 is 36249744866612.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21666844794263 - 2¹⁰ = 21666844793239 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21666844794193 and 21666844794202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21666844754263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10833422397131 + 10833422397132.

It is an arithmetic number, because the mean of its divisors is an integer number (10833422397132).

Almost surely, 2^{21666844794263} is an apocalyptic number.

21666844794263 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666844794263 is an equidigital number, since it uses as much as digits as its factorization.

21666844794263 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 501645312, while the sum is 68.

The spelling of 21666844794263 in words is "twenty-one trillion, six hundred sixty-six billion, eight hundred forty-four million, seven hundred ninety-four thousand, two hundred sixty-three".