666665555 has 4 divisors (see below), whose sum is σ = 799998672. Its totient is φ = 533332440.

The previous prime is 666665551. The next prime is 666665567. The reversal of 666665555 is 555566666.

It is a happy number.

666665555 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 666665555 - 2² = 666665551 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a zygodrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (666665551) 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, 66666551 + ... + 66666560.

It is an arithmetic number, because the mean of its divisors is an integer number (199999668).

Almost surely, 2^666665555 is an apocalyptic number.

666665555 is a deficient number, since it is larger than the sum of its proper divisors (133333117).

666665555 is a wasteful number, since it uses less digits than its factorization.

666665555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133333116.

The product of its digits is 4860000, while the sum is 50.

The square root of 666665555 is about 25819.8674473747. The cubic root of 666665555 is about 873.5799791709.

The spelling of 666665555 in words is "six hundred sixty-six million, six hundred sixty-five thousand, five hundred fifty-five".