686909 has 4 divisors (see below), whose sum is σ = 688800. Its totient is φ = 685020.

The previous prime is 686897. The next prime is 686911. The reversal of 686909 is 909686.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 909686 = 2 ⋅454843.

It is a cyclic number.

It is not a de Polignac number, because 686909 - 2⁴ = 686893 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686969) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 209 + ... + 1190.

It is an arithmetic number, because the mean of its divisors is an integer number (172200).

2⁶⁸⁶⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

686909 is a deficient number, since it is larger than the sum of its proper divisors (1891).

686909 is a wasteful number, since it uses less digits than its factorization.

686909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1890.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 686909 is about 828.7997345559. The cubic root of 686909 is about 88.2334110012.

The spelling of 686909 in words is "six hundred eighty-six thousand, nine hundred nine".