21165559417 has 2 divisors, whose sum is σ = 21165559418. Its totient is φ = 21165559416.

The previous prime is 21165559369. The next prime is 21165559421. The reversal of 21165559417 is 71495556112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18851564601 + 2313994816 = 137301^2 + 48104^2 .

It is a cyclic number.

It is not a de Polignac number, because 21165559417 - 2²⁷ = 21031341689 is a prime.

It is not a weakly prime, because it can be changed into another prime (21165559477) 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, 10582779708 + 10582779709.

It is an arithmetic number, because the mean of its divisors is an integer number (10582779709).

Almost surely, 2^21165559417 is an apocalyptic number.

It is an amenable number.

21165559417 is a deficient number, since it is larger than the sum of its proper divisors (1).

21165559417 is an equidigital number, since it uses as much as digits as its factorization.

21165559417 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 378000, while the sum is 46.

The spelling of 21165559417 in words is "twenty-one billion, one hundred sixty-five million, five hundred fifty-nine thousand, four hundred seventeen".