688391 has 4 divisors (see below), whose sum is σ = 750984. Its totient is φ = 625800.

The previous prime is 688379. The next prime is 688393. The reversal of 688391 is 193886.

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-688391 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688393) 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, 31280 + ... + 31301.

It is an arithmetic number, because the mean of its divisors is an integer number (187746).

2⁶⁸⁸³⁹¹ is an apocalyptic number.

688391 is a deficient number, since it is larger than the sum of its proper divisors (62593).

688391 is a wasteful number, since it uses less digits than its factorization.

688391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62592.

The product of its digits is 10368, while the sum is 35.

The square root of 688391 is about 829.6933168346. The cubic root of 688391 is about 88.2968196858.

The spelling of 688391 in words is "six hundred eighty-eight thousand, three hundred ninety-one".