684391 has 4 divisors (see below), whose sum is σ = 687312. Its totient is φ = 681472.

The previous prime is 684379. The next prime is 684407. The reversal of 684391 is 193486.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-684391 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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 (684311) 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, 1075 + ... + 1588.

It is an arithmetic number, because the mean of its divisors is an integer number (171828).

2⁶⁸⁴³⁹¹ is an apocalyptic number.

684391 is a deficient number, since it is larger than the sum of its proper divisors (2921).

684391 is a wasteful number, since it uses less digits than its factorization.

684391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2920.

The product of its digits is 5184, while the sum is 31.

The square root of 684391 is about 827.2792756984. The cubic root of 684391 is about 88.1254666910.

The spelling of 684391 in words is "six hundred eighty-four thousand, three hundred ninety-one".