666728 has 8 divisors (see below), whose sum is σ = 1250130. Its totient is φ = 333360.

The previous prime is 666727. The next prime is 666733. The reversal of 666728 is 827666.

It can be written as a sum of positive squares in only one way, i.e., 438244 + 228484 = 662^2 + 478^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (666727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41663 + ... + 41678.

2⁶⁶⁶⁷²⁸ is an apocalyptic number.

It is an amenable number.

666728 is a deficient number, since it is larger than the sum of its proper divisors (583402).

666728 is a wasteful number, since it uses less digits than its factorization.

666728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83347 (or 83343 counting only the distinct ones).

The product of its digits is 24192, while the sum is 35.

The square root of 666728 is about 816.5341389066. The cubic root of 666728 is about 87.3607253716.

The spelling of 666728 in words is "six hundred sixty-six thousand, seven hundred twenty-eight".