666555 has 16 divisors (see below), whose sum is σ = 1096224. Its totient is φ = 345600.

The previous prime is 666541. The next prime is 666557. The reversal of 666555 is 555666.

It is not a de Polignac number, because 666555 - 2⁷ = 666427 is a prime.

It is a nialpdrome in base 7 and base 10.

It is a zygodrome in base 10.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 666555.

It is not an unprimeable number, because it can be changed into a prime (666557) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46 + ... + 1155.

It is an arithmetic number, because the mean of its divisors is an integer number (68514).

2⁶⁶⁶⁵⁵⁵ is an apocalyptic number.

666555 is a deficient number, since it is larger than the sum of its proper divisors (429669).

666555 is a wasteful number, since it uses less digits than its factorization.

666555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1246.

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

The square root of 666555 is about 816.4281964754. The cubic root of 666555 is about 87.3531687103.

Adding to 666555 its reverse (555666), we get a palindrome (1222221).

Subtracting from 666555 its reverse (555666), we obtain a square (110889 = 333²).

It can be divided in two parts, 666 and 555, that added together give a palindrome (1221).

The spelling of 666555 in words is "six hundred sixty-six thousand, five hundred fifty-five".