665613 has 12 divisors (see below), whose sum is σ = 1035580. Its totient is φ = 409536.

The previous prime is 665603. The next prime is 665617. The reversal of 665613 is 316566.

665613 is a `hidden beast` number, since 6 + 656 + 1 + 3 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 393129 + 272484 = 627^2 + 522^2 .

It is not a de Polignac number, because 665613 - 2⁶ = 665549 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665617) by changing a digit.

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, 2728 + ... + 2961.

2⁶⁶⁵⁶¹³ is an apocalyptic number.

It is an amenable number.

665613 is a deficient number, since it is larger than the sum of its proper divisors (369967).

665613 is a wasteful number, since it uses less digits than its factorization.

665613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5708 (or 5705 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 665613 is about 815.8510893539. The cubic root of 665613 is about 87.3119990750.

It can be divided in two parts, 66561 and 3, that added together give a square (66564 = 258²).

The spelling of 665613 in words is "six hundred sixty-five thousand, six hundred thirteen".