666709399 has 2 divisors, whose sum is σ = 666709400. Its totient is φ = 666709398.

The previous prime is 666709387. The next prime is 666709423. The reversal of 666709399 is 993907666.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666709399 - 2²⁵ = 633154967 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666709319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333354699 + 333354700.

It is an arithmetic number, because the mean of its divisors is an integer number (333354700).

Almost surely, 2^666709399 is an apocalyptic number.

666709399 is a deficient number, since it is larger than the sum of its proper divisors (1).

666709399 is an equidigital number, since it uses as much as digits as its factorization.

666709399 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3306744, while the sum is 55.

The square root of 666709399 is about 25820.7164695328. The cubic root of 666709399 is about 873.5991294033.

The spelling of 666709399 in words is "six hundred sixty-six million, seven hundred nine thousand, three hundred ninety-nine".