665765 has 4 divisors (see below), whose sum is σ = 798924. Its totient is φ = 532608.

The previous prime is 665761. The next prime is 665773. The reversal of 665765 is 567566.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 145924 + 519841 = 382^2 + 721^2 .

It is a cyclic number.

It is not a de Polignac number, because 665765 - 2² = 665761 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665761) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66572 + ... + 66581.

It is an arithmetic number, because the mean of its divisors is an integer number (199731).

2⁶⁶⁵⁷⁶⁵ is an apocalyptic number.

It is an amenable number.

665765 is a deficient number, since it is larger than the sum of its proper divisors (133159).

665765 is a wasteful number, since it uses less digits than its factorization.

665765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133158.

The product of its digits is 37800, while the sum is 35.

The square root of 665765 is about 815.9442382908. The cubic root of 665765 is about 87.3186447854.

The spelling of 665765 in words is "six hundred sixty-five thousand, seven hundred sixty-five".