686784 has 84 divisors (see below), whose sum is σ = 2142744. Its totient is φ = 193536.

The previous prime is 686773. The next prime is 686789. The reversal of 686784 is 487686.

It is a tau number, because it is divible by the number of its divisors (84).

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686789) 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, 9372 + ... + 9444.

2⁶⁸⁶⁷⁸⁴ is an apocalyptic number.

686784 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 686784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1071372).

686784 is an abundant number, since it is smaller than the sum of its proper divisors (1455960).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

686784 is a wasteful number, since it uses less digits than its factorization.

686784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102 (or 85 counting only the distinct ones).

The product of its digits is 64512, while the sum is 39.

The square root of 686784 is about 828.7243208691. The cubic root of 686784 is about 88.2280585962.

It can be divided in two parts, 686 and 784, that multiplied together give a 5-th power (537824 = 14⁵).

The spelling of 686784 in words is "six hundred eighty-six thousand, seven hundred eighty-four".