665556 has 24 divisors (see below), whose sum is σ = 1596000. Its totient is φ = 215712.

The previous prime is 665549. The next prime is 665557. The reversal of 665556 is 655566.

665556 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a plaindrome in base 14.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 306 + ... + 1193.

It is an arithmetic number, because the mean of its divisors is an integer number (66500).

2⁶⁶⁵⁵⁵⁶ is an apocalyptic number.

It is an amenable number.

665556 is an abundant number, since it is smaller than the sum of its proper divisors (930444).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

665556 is a wasteful number, since it uses less digits than its factorization.

665556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1543 (or 1541 counting only the distinct ones).

The product of its digits is 27000, while the sum is 33.

The square root of 665556 is about 815.8161557606. The cubic root of 665556 is about 87.3095066727.

It can be divided in two parts, 665 and 556, that added together give a palindrome (1221).

The spelling of 665556 in words is "six hundred sixty-five thousand, five hundred fifty-six".