665656399 has 2 divisors, whose sum is σ = 665656400. Its totient is φ = 665656398.

The previous prime is 665656379. The next prime is 665656423. The reversal of 665656399 is 993656566.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 665656399 - 2⁵ = 665656367 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665656319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332828199 + 332828200.

It is an arithmetic number, because the mean of its divisors is an integer number (332828200).

Almost surely, 2^665656399 is an apocalyptic number.

665656399 is a deficient number, since it is larger than the sum of its proper divisors (1).

665656399 is an equidigital number, since it uses as much as digits as its factorization.

665656399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7873200, while the sum is 55.

The square root of 665656399 is about 25800.3178081201. The cubic root of 665656399 is about 873.1389665966.

The spelling of 665656399 in words is "six hundred sixty-five million, six hundred fifty-six thousand, three hundred ninety-nine".