686663 has 4 divisors (see below), whose sum is σ = 693840. Its totient is φ = 679488.

The previous prime is 686639. The next prime is 686669. The reversal of 686663 is 366686.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 366686 = 2 ⋅183343.

It is a cyclic number.

It is not a de Polignac number, because 686663 - 2¹⁴ = 670279 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 (686669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3443 + ... + 3636.

It is an arithmetic number, because the mean of its divisors is an integer number (173460).

2⁶⁸⁶⁶⁶³ is an apocalyptic number.

686663 is a deficient number, since it is larger than the sum of its proper divisors (7177).

686663 is an equidigital number, since it uses as much as digits as its factorization.

686663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7176.

The product of its digits is 31104, while the sum is 35.

The square root of 686663 is about 828.6513138830. The cubic root of 686663 is about 88.2228768496. Note that the first 3 decimals are identical.

The spelling of 686663 in words is "six hundred eighty-six thousand, six hundred sixty-three".