665696640 has 128 divisors (see below), whose sum is σ = 2425086720. Its totient is φ = 152156160.

The previous prime is 665696621. The next prime is 665696663. The reversal of 665696640 is 46696566.

It is a happy number.

665696640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 665696640.

It is a congruent number.

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, 11326 + ... + 38205.

It is an arithmetic number, because the mean of its divisors is an integer number (18945990).

Almost surely, 2^665696640 is an apocalyptic number.

665696640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

665696640 is an abundant number, since it is smaller than the sum of its proper divisors (1759390080).

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

665696640 is a wasteful number, since it uses less digits than its factorization.

665696640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49560 (or 49548 counting only the distinct ones).

The product of its (nonzero) digits is 1399680, while the sum is 48.

The square root of 665696640 is about 25801.0976510690. The cubic root of 665696640 is about 873.1565608976.

The spelling of 665696640 in words is "six hundred sixty-five million, six hundred ninety-six thousand, six hundred forty".