728009 has 4 divisors (see below), whose sum is σ = 732804. Its totient is φ = 723216.

The previous prime is 728003. The next prime is 728017. The reversal of 728009 is 900827.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 900827 = 29 ⋅31063.

It can be written as a sum of positive squares in 2 ways, for example, as 198025 + 529984 = 445^2 + 728^2 .

It is a cyclic number.

It is not a de Polignac number, because 728009 - 2¹² = 723913 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (728003) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 2162 + ... + 2475.

It is an arithmetic number, because the mean of its divisors is an integer number (183201).

2⁷²⁸⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

728009 is a deficient number, since it is larger than the sum of its proper divisors (4795).

728009 is a wasteful number, since it uses less digits than its factorization.

728009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4794.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 728009 is about 853.2344343731. The cubic root of 728009 is about 89.9591996134.

The spelling of 728009 in words is "seven hundred twenty-eight thousand, nine".