665865 has 12 divisors (see below), whose sum is σ = 1154244. Its totient is φ = 355104.

The previous prime is 665857. The next prime is 665897. The reversal of 665865 is 568566.

It can be written as a sum of positive squares in 2 ways, for example, as 242064 + 423801 = 492^2 + 651^2 .

It is not a de Polignac number, because 665865 - 2³ = 665857 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7354 + ... + 7443.

It is an arithmetic number, because the mean of its divisors is an integer number (96187).

2⁶⁶⁵⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

665865 is a deficient number, since it is larger than the sum of its proper divisors (488379).

665865 is a wasteful number, since it uses less digits than its factorization.

665865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14808 (or 14805 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 665865 is about 816.0055146872. The cubic root of 665865 is about 87.3230164117.

The spelling of 665865 in words is "six hundred sixty-five thousand, eight hundred sixty-five".