665691728 has 40 divisors (see below), whose sum is σ = 1390572456. Its totient is φ = 306892800.

The previous prime is 665691721. The next prime is 665691731. The reversal of 665691728 is 827196566.

665691728 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 33269824 + 632421904 = 5768^2 + 25148^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665691721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 306968 + ... + 309128.

Almost surely, 2^665691728 is an apocalyptic number.

It is an amenable number.

665691728 is an abundant number, since it is smaller than the sum of its proper divisors (724880728).

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

665691728 is a wasteful number, since it uses less digits than its factorization.

665691728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3663 (or 3657 counting only the distinct ones).

The product of its digits is 1088640, while the sum is 50.

The square root of 665691728 is about 25801.0024611448. The cubic root of 665691728 is about 873.1544132950.

The spelling of 665691728 in words is "six hundred sixty-five million, six hundred ninety-one thousand, seven hundred twenty-eight".