686591 has 4 divisors (see below), whose sum is σ = 693000. Its totient is φ = 680184.

The previous prime is 686563. The next prime is 686593. The reversal of 686591 is 195686.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 195686 = 2 ⋅97843.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-686591 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 (686593) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3041 + ... + 3258.

It is an arithmetic number, because the mean of its divisors is an integer number (173250).

2⁶⁸⁶⁵⁹¹ is an apocalyptic number.

686591 is a deficient number, since it is larger than the sum of its proper divisors (6409).

686591 is a wasteful number, since it uses less digits than its factorization.

686591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6408.

The product of its digits is 12960, while the sum is 35.

The square root of 686591 is about 828.6078686568. The cubic root of 686591 is about 88.2197932073.

The spelling of 686591 in words is "six hundred eighty-six thousand, five hundred ninety-one".