665605639 has 2 divisors, whose sum is σ = 665605640. Its totient is φ = 665605638.

The previous prime is 665605637. The next prime is 665605693. The reversal of 665605639 is 936506566.

665605639 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

Together with next prime (665605693) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 665605639 - 2¹ = 665605637 is a prime.

Together with 665605637, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665605637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332802819 + 332802820.

It is an arithmetic number, because the mean of its divisors is an integer number (332802820).

Almost surely, 2^665605639 is an apocalyptic number.

665605639 is a deficient number, since it is larger than the sum of its proper divisors (1).

665605639 is an equidigital number, since it uses as much as digits as its factorization.

665605639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 874800, while the sum is 46.

The square root of 665605639 is about 25799.3340805533. The cubic root of 665605639 is about 873.1167721328.

The spelling of 665605639 in words is "six hundred sixty-five million, six hundred five thousand, six hundred thirty-nine".