686664 has 96 divisors (see below), whose sum is σ = 2210400. Its totient is φ = 195840.

The previous prime is 686639. The next prime is 686669. The reversal of 686664 is 466686.

It is a Harshad number since it is a multiple of its sum of digits (36).

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

It is not an unprimeable number, because it can be changed into a prime (686669) by changing a digit.

686664 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 40384 + ... + 40400.

It is an arithmetic number, because the mean of its divisors is an integer number (23025).

2⁶⁸⁶⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 686664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1105200).

686664 is an abundant number, since it is smaller than the sum of its proper divisors (1523736).

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

686664 is a wasteful number, since it uses less digits than its factorization.

686664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60 (or 33 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 686664 is about 828.6519172729. The cubic root of 686664 is about 88.2229196764. Note that the first 3 decimals are identical.

The spelling of 686664 in words is "six hundred eighty-six thousand, six hundred sixty-four".