21259166717 has 2 divisors, whose sum is σ = 21259166718. Its totient is φ = 21259166716.

The previous prime is 21259166713. The next prime is 21259166771. The reversal of 21259166717 is 71766195212.

Together with next prime (21259166771) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21174324196 + 84842521 = 145514^2 + 9211^2 .

It is a cyclic number.

It is not a de Polignac number, because 21259166717 - 2² = 21259166713 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21259166711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10629583358 + 10629583359.

It is an arithmetic number, because the mean of its divisors is an integer number (10629583359).

Almost surely, 2^21259166717 is an apocalyptic number.

It is an amenable number.

21259166717 is a deficient number, since it is larger than the sum of its proper divisors (1).

21259166717 is an equidigital number, since it uses as much as digits as its factorization.

21259166717 is an evil number, because the sum of its binary digits is even.

The product of its digits is 317520, while the sum is 47.

The spelling of 21259166717 in words is "twenty-one billion, two hundred fifty-nine million, one hundred sixty-six thousand, seven hundred seventeen".