665509 has 4 divisors (see below), whose sum is σ = 716716. Its totient is φ = 614304.

The previous prime is 665507. The next prime is 665527. The reversal of 665509 is 905566.

It is a happy number.

665509 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 49284 + 616225 = 222^2 + 785^2 .

It is a cyclic number.

It is not a de Polignac number, because 665509 - 2¹ = 665507 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665501) 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, 25584 + ... + 25609.

It is an arithmetic number, because the mean of its divisors is an integer number (179179).

2⁶⁶⁵⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

665509 is a deficient number, since it is larger than the sum of its proper divisors (51207).

665509 is a wasteful number, since it uses less digits than its factorization.

665509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51206.

The product of its (nonzero) digits is 8100, while the sum is 31.

The square root of 665509 is about 815.7873497426. The cubic root of 665509 is about 87.3074514270.

The spelling of 665509 in words is "six hundred sixty-five thousand, five hundred nine".