686709 has 12 divisors (see below), whose sum is σ = 1016652. Its totient is φ = 446400.

The previous prime is 686687. The next prime is 686723. The reversal of 686709 is 907686.

It can be written as a sum of positive squares in 2 ways, for example, as 11025 + 675684 = 105^2 + 822^2 .

It is not a de Polignac number, because 686709 - 2⁸ = 686453 is a prime.

It is a Curzon number.

686709 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686729) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 562 + ... + 1299.

It is an arithmetic number, because the mean of its divisors is an integer number (84721).

2⁶⁸⁶⁷⁰⁹ is an apocalyptic number.

It is an amenable number.

686709 is a deficient number, since it is larger than the sum of its proper divisors (329943).

686709 is a wasteful number, since it uses less digits than its factorization.

686709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1908 (or 1905 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 686709 is about 828.6790693628. The cubic root of 686709 is about 88.2248468415.

The spelling of 686709 in words is "six hundred eighty-six thousand, seven hundred nine".