666865 has 8 divisors (see below), whose sum is σ = 820008. Its totient is φ = 520320.

The previous prime is 666857. The next prime is 666871. The reversal of 666865 is 568666.

666865 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 99856 + 567009 = 316^2 + 753^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 666865 - 2³ = 666857 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1422 + ... + 1831.

It is an arithmetic number, because the mean of its divisors is an integer number (102501).

2⁶⁶⁶⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

666865 is a deficient number, since it is larger than the sum of its proper divisors (153143).

666865 is a wasteful number, since it uses less digits than its factorization.

666865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3299.

The product of its digits is 51840, while the sum is 37.

The square root of 666865 is about 816.6180257624. The cubic root of 666865 is about 87.3667086210.

The spelling of 666865 in words is "six hundred sixty-six thousand, eight hundred sixty-five".