21209984243017 has 2 divisors, whose sum is σ = 21209984243018. Its totient is φ = 21209984243016.

The previous prime is 21209984243009. The next prime is 21209984243039. The reversal of 21209984243017 is 71034248990212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11140348096656 + 10069636146361 = 3337716^2 + 3173269^2 .

It is a cyclic number.

It is not a de Polignac number, because 21209984243017 - 2³ = 21209984243009 is a prime.

It is not a weakly prime, because it can be changed into another prime (21209984247017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10604992121508 + 10604992121509.

It is an arithmetic number, because the mean of its divisors is an integer number (10604992121509).

Almost surely, 2^{21209984243017} is an apocalyptic number.

It is an amenable number.

21209984243017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21209984243017 is an equidigital number, since it uses as much as digits as its factorization.

21209984243017 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1741824, while the sum is 52.

The spelling of 21209984243017 in words is "twenty-one trillion, two hundred nine billion, nine hundred eighty-four million, two hundred forty-three thousand, seventeen".