728661 has 4 divisors (see below), whose sum is σ = 971552. Its totient is φ = 485772.

The previous prime is 728659. The next prime is 728681. The reversal of 728661 is 166827.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 166827 = 3 ⋅55609.

It is not a de Polignac number, because 728661 - 2¹ = 728659 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (728681) 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, 121441 + ... + 121446.

It is an arithmetic number, because the mean of its divisors is an integer number (242888).

2⁷²⁸⁶⁶¹ is an apocalyptic number.

It is an amenable number.

728661 is a deficient number, since it is larger than the sum of its proper divisors (242891).

728661 is a wasteful number, since it uses less digits than its factorization.

728661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242890.

The product of its digits is 4032, while the sum is 30.

The square root of 728661 is about 853.6164243968. The cubic root of 728661 is about 89.9860472197.

The spelling of 728661 in words is "seven hundred twenty-eight thousand, six hundred sixty-one".