687728 has 20 divisors (see below), whose sum is σ = 1359288. Its totient is φ = 336960.

The previous prime is 687721. The next prime is 687737. The reversal of 687728 is 827786.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 687691 and 687700.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (687721) by changing a digit.

687728 is an untouchable number, because it is not equal to the sum of proper divisors of any 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 in 3 ways as a sum of consecutive naturals, for example, 443 + ... + 1253.

2⁶⁸⁷⁷²⁸ is an apocalyptic number.

It is an amenable number.

687728 is a deficient number, since it is larger than the sum of its proper divisors (671560).

687728 is a wasteful number, since it uses less digits than its factorization.

687728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 872 (or 866 counting only the distinct ones).

The product of its digits is 37632, while the sum is 38.

The square root of 687728 is about 829.2936753648. The cubic root of 687728 is about 88.2684639038.

The spelling of 687728 in words is "six hundred eighty-seven thousand, seven hundred twenty-eight".