665390639 has 2 divisors, whose sum is σ = 665390640. Its totient is φ = 665390638.

The previous prime is 665390617. The next prime is 665390651. The reversal of 665390639 is 936093566.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 665390639 - 2²⁴ = 648613423 is a prime.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 665390593 and 665390602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665390689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332695319 + 332695320.

It is an arithmetic number, because the mean of its divisors is an integer number (332695320).

Almost surely, 2^665390639 is an apocalyptic number.

665390639 is a deficient number, since it is larger than the sum of its proper divisors (1).

665390639 is an equidigital number, since it uses as much as digits as its factorization.

665390639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 787320, while the sum is 47.

The square root of 665390639 is about 25795.1669698027. The cubic root of 665390639 is about 873.0227523355.

The spelling of 665390639 in words is "six hundred sixty-five million, three hundred ninety thousand, six hundred thirty-nine".