686631 has 8 divisors (see below), whose sum is σ = 998784. Its totient is φ = 416120.

The previous prime is 686611. The next prime is 686639. The reversal of 686631 is 136686.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 686631 - 2⁷ = 686503 is a prime.

It is a super-2 number, since 2×686631² = 942924260322, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686639) 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 7 ways as a sum of consecutive naturals, for example, 10371 + ... + 10436.

It is an arithmetic number, because the mean of its divisors is an integer number (124848).

2⁶⁸⁶⁶³¹ is an apocalyptic number.

686631 is a deficient number, since it is larger than the sum of its proper divisors (312153).

686631 is a wasteful number, since it uses less digits than its factorization.

686631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20821.

The product of its digits is 5184, while the sum is 30.

The square root of 686631 is about 828.6320051748. The cubic root of 686631 is about 88.2215063685.

Subtracting from 686631 its reverse (136686), we obtain a palindrome (549945).

The spelling of 686631 in words is "six hundred eighty-six thousand, six hundred thirty-one".