681728 has 18 divisors (see below), whose sum is σ = 1361304. Its totient is φ = 340736.

The previous prime is 681727. The next prime is 681731. The reversal of 681728 is 827186.

681728 is nontrivially palindromic in base 7.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 681694 and 681703.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1076 + ... + 1587.

It is an arithmetic number, because the mean of its divisors is an integer number (75628).

2⁶⁸¹⁷²⁸ is an apocalyptic number.

It is an amenable number.

681728 is a deficient number, since it is larger than the sum of its proper divisors (679576).

681728 is an equidigital number, since it uses as much as digits as its factorization.

681728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2679 (or 2665 counting only the distinct ones).

The product of its digits is 5376, while the sum is 32.

The square root of 681728 is about 825.6682142362. The cubic root of 681728 is about 88.0110179042.

The spelling of 681728 in words is "six hundred eighty-one thousand, seven hundred twenty-eight".