665647399 has 2 divisors, whose sum is σ = 665647400. Its totient is φ = 665647398.

The previous prime is 665647379. The next prime is 665647453. The reversal of 665647399 is 993746566.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 665647399 - 2¹⁹ = 665123111 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665647319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332823699 + 332823700.

It is an arithmetic number, because the mean of its divisors is an integer number (332823700).

Almost surely, 2^665647399 is an apocalyptic number.

665647399 is a deficient number, since it is larger than the sum of its proper divisors (1).

665647399 is an equidigital number, since it uses as much as digits as its factorization.

665647399 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7348320, while the sum is 55.

The square root of 665647399 is about 25800.1433910744. The cubic root of 665647399 is about 873.1350314903.

It can be divided in two parts, 66 and 5647399, that added together give a palindrome (5647465).

The spelling of 665647399 in words is "six hundred sixty-five million, six hundred forty-seven thousand, three hundred ninety-nine".