664726656 has 128 divisors (see below), whose sum is σ = 2039722560. Its totient is φ = 189562880.

The previous prime is 664726607. The next prime is 664726669. The reversal of 664726656 is 656627466.

664726656 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 an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 67180 + ... + 76436.

Almost surely, 2^664726656 is an apocalyptic number.

664726656 is a gapful number since it is divisible by the number (66) 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 664726656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1019861280).

664726656 is an abundant number, since it is smaller than the sum of its proper divisors (1374995904).

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

664726656 is a wasteful number, since it uses less digits than its factorization.

664726656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9302 (or 9290 counting only the distinct ones).

The product of its digits is 2177280, while the sum is 48.

The square root of 664726656 is about 25782.2934588838. The cubic root of 664726656 is about 872.7322637341.

The spelling of 664726656 in words is "six hundred sixty-four million, seven hundred twenty-six thousand, six hundred fifty-six".