728666 has 4 divisors (see below), whose sum is σ = 1093002. Its totient is φ = 364332.

The previous prime is 728659. The next prime is 728681. The reversal of 728666 is 666827.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 666827 = 7 ⋅95261.

It can be written as a sum of positive squares in only one way, i.e., 714025 + 14641 = 845^2 + 121^2 .

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 182165 + ... + 182168.

2⁷²⁸⁶⁶⁶ is an apocalyptic number.

728666 is a deficient number, since it is larger than the sum of its proper divisors (364336).

728666 is a wasteful number, since it uses less digits than its factorization.

728666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 364335.

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

The square root of 728666 is about 853.6193531077. The cubic root of 728666 is about 89.9862530444.

The spelling of 728666 in words is "seven hundred twenty-eight thousand, six hundred sixty-six".