665939 has 4 divisors (see below), whose sum is σ = 667656. Its totient is φ = 664224.

The previous prime is 665923. The next prime is 665947. The reversal of 665939 is 939566.

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

It is a cyclic number.

It is not a de Polignac number, because 665939 - 2⁴ = 665923 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665039) 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, 32 + ... + 1154.

It is an arithmetic number, because the mean of its divisors is an integer number (166914).

2⁶⁶⁵⁹³⁹ is an apocalyptic number.

665939 is a deficient number, since it is larger than the sum of its proper divisors (1717).

665939 is a wasteful number, since it uses less digits than its factorization.

665939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1716.

The product of its digits is 43740, while the sum is 38.

The square root of 665939 is about 816.0508562584. The cubic root of 665939 is about 87.3262511334.

The spelling of 665939 in words is "six hundred sixty-five thousand, nine hundred thirty-nine".