666385 has 4 divisors (see below), whose sum is σ = 799668. Its totient is φ = 533104.

The previous prime is 666353. The next prime is 666403. The reversal of 666385 is 583666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 583666 = 2 ⋅291833.

It can be written as a sum of positive squares in 2 ways, for example, as 258064 + 408321 = 508^2 + 639^2 .

It is a cyclic number.

It is not a de Polignac number, because 666385 - 2⁵ = 666353 is a prime.

It is a Duffinian number.

666385 is a lucky number.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 666385.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66634 + ... + 66643.

It is an arithmetic number, because the mean of its divisors is an integer number (199917).

2⁶⁶⁶³⁸⁵ is an apocalyptic number.

It is an amenable number.

666385 is a deficient number, since it is larger than the sum of its proper divisors (133283).

666385 is a wasteful number, since it uses less digits than its factorization.

666385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133282.

The product of its digits is 25920, while the sum is 34.

The square root of 666385 is about 816.3240778024. The cubic root of 666385 is about 87.3457418157.

The spelling of 666385 in words is "six hundred sixty-six thousand, three hundred eighty-five".