691728 has 20 divisors (see below), whose sum is σ = 1787088. Its totient is φ = 230560.

The previous prime is 691727. The next prime is 691729. The reversal of 691728 is 827196.

It is an interprime number because it is at equal distance from previous prime (691727) and next prime (691729).

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (691721) 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 in 3 ways as a sum of consecutive naturals, for example, 7158 + ... + 7253.

2⁶⁹¹⁷²⁸ is an apocalyptic number.

It is an amenable number.

691728 is an abundant number, since it is smaller than the sum of its proper divisors (1095360).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

691728 is a wasteful number, since it uses less digits than its factorization.

691728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14422 (or 14416 counting only the distinct ones).

The product of its digits is 6048, while the sum is 33.

The square root of 691728 is about 831.7018696624. The cubic root of 691728 is about 88.4392637630.

The spelling of 691728 in words is "six hundred ninety-one thousand, seven hundred twenty-eight".