643604208209 has 2 divisors, whose sum is σ = 643604208210. Its totient is φ = 643604208208.

The previous prime is 643604208151. The next prime is 643604208229. The reversal of 643604208209 is 902802406346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 641165329984 + 2438878225 = 800728^2 + 49385^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643604208209 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 643604208209.

It is not a weakly prime, because it can be changed into another prime (643604208229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321802104104 + 321802104105.

It is an arithmetic number, because the mean of its divisors is an integer number (321802104105).

Almost surely, 2^643604208209 is an apocalyptic number.

It is an amenable number.

643604208209 is a deficient number, since it is larger than the sum of its proper divisors (1).

643604208209 is an equidigital number, since it uses as much as digits as its factorization.

643604208209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 497664, while the sum is 44.

The spelling of 643604208209 in words is "six hundred forty-three billion, six hundred four million, two hundred eight thousand, two hundred nine".