665556640 has 96 divisors (see below), whose sum is σ = 1806900480. Its totient is φ = 226934784.

The previous prime is 665556637. The next prime is 665556677. The reversal of 665556640 is 46655566.

665556640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 214621 + ... + 217699.

It is an arithmetic number, because the mean of its divisors is an integer number (18821880).

Almost surely, 2^665556640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665556640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (903450240).

665556640 is an abundant number, since it is smaller than the sum of its proper divisors (1141343840).

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

665556640 is a wasteful number, since it uses less digits than its factorization.

665556640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3294 (or 3286 counting only the distinct ones).

The product of its (nonzero) digits is 648000, while the sum is 43.

The square root of 665556640 is about 25798.3844455423. The cubic root of 665556640 is about 873.0953465839.

The spelling of 665556640 in words is "six hundred sixty-five million, five hundred fifty-six thousand, six hundred forty".