668764728 has 64 divisors (see below), whose sum is σ = 1872384000. Its totient is φ = 221157216.

The previous prime is 668764703. The next prime is 668764729. The reversal of 668764728 is 827467866.

668764728 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×668764728² = 894492522833827968, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668764729) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15243 + ... + 39621.

It is an arithmetic number, because the mean of its divisors is an integer number (29256000).

Almost surely, 2^668764728 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 668764728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (936192000).

668764728 is an abundant number, since it is smaller than the sum of its proper divisors (1203619272).

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

668764728 is a wasteful number, since it uses less digits than its factorization.

668764728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24521 (or 24511 counting only the distinct ones).

The product of its digits is 5419008, while the sum is 54.

The square root of 668764728 is about 25860.4858423039. The cubic root of 668764728 is about 874.4959177659.

The spelling of 668764728 in words is "six hundred sixty-eight million, seven hundred sixty-four thousand, seven hundred twenty-eight".