666439 has 2 divisors, whose sum is σ = 666440. Its totient is φ = 666438.

The previous prime is 666437. The next prime is 666461. The reversal of 666439 is 934666.

666439 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666439 - 2¹ = 666437 is a prime.

Together with 666437, 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 (666431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333219 + 333220.

It is an arithmetic number, because the mean of its divisors is an integer number (333220).

2⁶⁶⁶⁴³⁹ is an apocalyptic number.

666439 is a deficient number, since it is larger than the sum of its proper divisors (1).

666439 is an equidigital number, since it uses as much as digits as its factorization.

666439 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23328, while the sum is 34.

The square root of 666439 is about 816.3571522318. The cubic root of 666439 is about 87.3481010838.

The spelling of 666439 in words is "six hundred sixty-six thousand, four hundred thirty-nine".