665559 has 6 divisors (see below), whose sum is σ = 961376. Its totient is φ = 443700.

The previous prime is 665557. The next prime is 665563. The reversal of 665559 is 955566.

It is not a de Polignac number, because 665559 - 2¹ = 665557 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 665559.

It is not an unprimeable number, because it can be changed into a prime (665557) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36967 + ... + 36984.

2⁶⁶⁵⁵⁵⁹ is an apocalyptic number.

665559 is a deficient number, since it is larger than the sum of its proper divisors (295817).

665559 is a wasteful number, since it uses less digits than its factorization.

665559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73957 (or 73954 counting only the distinct ones).

The product of its digits is 40500, while the sum is 36.

The square root of 665559 is about 815.8179944081. The cubic root of 665559 is about 87.3096378553.

It can be divided in two parts, 66555 and 9, that added together give a square (66564 = 258²).

The spelling of 665559 in words is "six hundred sixty-five thousand, five hundred fifty-nine".