665708602721 has 2 divisors, whose sum is σ = 665708602722. Its totient is φ = 665708602720.

The previous prime is 665708602717. The next prime is 665708602723. The reversal of 665708602721 is 127206807566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 412131900625 + 253576702096 = 641975^2 + 503564^2 .

It is a cyclic number.

It is not a de Polignac number, because 665708602721 - 2² = 665708602717 is a prime.

Together with 665708602723, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 665708602721.

It is not a weakly prime, because it can be changed into another prime (665708602723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332854301360 + 332854301361.

It is an arithmetic number, because the mean of its divisors is an integer number (332854301361).

Almost surely, 2^665708602721 is an apocalyptic number.

It is an amenable number.

665708602721 is a deficient number, since it is larger than the sum of its proper divisors (1).

665708602721 is an equidigital number, since it uses as much as digits as its factorization.

665708602721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1693440, while the sum is 50.

The spelling of 665708602721 in words is "six hundred sixty-five billion, seven hundred eight million, six hundred two thousand, seven hundred twenty-one".