664688640 has 384 divisors, whose sum is σ = 2660636160. Its totient is φ = 137625600.

The previous prime is 664688623. The next prime is 664688669. The reversal of 664688640 is 46886466.

664688640 is digitally balanced in base 6, 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 (384).

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 664688640.

It is a Saint-Exupery number, since it is equal to the product of the sides of a Pythagorean triangle: 1124 × 924 × 640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2365300 + ... + 2365580.

It is an arithmetic number, because the mean of its divisors is an integer number (6928740).

Almost surely, 2^664688640 is an apocalyptic number.

664688640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 664688640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1330318080).

664688640 is an abundant number, since it is smaller than the sum of its proper divisors (1995947520).

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

664688640 is a wasteful number, since it uses less digits than its factorization.

664688640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329 (or 309 counting only the distinct ones).

The product of its (nonzero) digits is 1327104, while the sum is 48.

The square root of 664688640 is about 25781.5561981817. The cubic root of 664688640 is about 872.7156261072.

It can be divided in two parts, 6 and 64688640, that added together give a palindrome (64688646).

The spelling of 664688640 in words is "six hundred sixty-four million, six hundred eighty-eight thousand, six hundred forty".