665806 has 4 divisors (see below), whose sum is σ = 998712. Its totient is φ = 332902.

The previous prime is 665803. The next prime is 665813. The reversal of 665806 is 608566.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166450 + ... + 166453.

It is an arithmetic number, because the mean of its divisors is an integer number (249678).

2⁶⁶⁵⁸⁰⁶ is an apocalyptic number.

665806 is a deficient number, since it is larger than the sum of its proper divisors (332906).

665806 is a wasteful number, since it uses less digits than its factorization.

665806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332905.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 665806 is about 815.9693621699. The cubic root of 665806 is about 87.3204372051.

The spelling of 665806 in words is "six hundred sixty-five thousand, eight hundred six".