665506655 has 20 divisors (see below), whose sum is σ = 878559960. Its totient is φ = 483951600.

The previous prime is 665506649. The next prime is 665506687. The reversal of 665506655 is 556605566.

It is not a de Polignac number, because 665506655 - 2⁶ = 665506591 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 68660 + ... + 77750.

It is an arithmetic number, because the mean of its divisors is an integer number (43927998).

Almost surely, 2^665506655 is an apocalyptic number.

665506655 is a deficient number, since it is larger than the sum of its proper divisors (213053305).

665506655 is an frugal number, since it uses more digits than its factorization.

665506655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9140 (or 9107 counting only the distinct ones).

The product of its (nonzero) digits is 810000, while the sum is 44.

The square root of 665506655 is about 25797.4156651398. The cubic root of 665506655 is about 873.0734888081.

Adding to 665506655 its reverse (556605566), we get a palindrome (1222112221).

The spelling of 665506655 in words is "six hundred sixty-five million, five hundred six thousand, six hundred fifty-five".