686531 has 4 divisors (see below), whose sum is σ = 688200. Its totient is φ = 684864.

The previous prime is 686519. The next prime is 686551. The reversal of 686531 is 135686.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 135686 = 2 ⋅67843.

It is a cyclic number.

It is not a de Polignac number, because 686531 - 2¹⁴ = 670147 is a prime.

It is a super-2 number, since 2×686531² = 942649627922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 686494 and 686503.

It is not an unprimeable number, because it can be changed into a prime (686551) 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, 275 + ... + 1203.

It is an arithmetic number, because the mean of its divisors is an integer number (172050).

2⁶⁸⁶⁵³¹ is an apocalyptic number.

686531 is a deficient number, since it is larger than the sum of its proper divisors (1669).

686531 is an equidigital number, since it uses as much as digits as its factorization.

686531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1668.

The product of its digits is 4320, while the sum is 29.

The square root of 686531 is about 828.5716625615. The cubic root of 686531 is about 88.2172233407.

The spelling of 686531 in words is "six hundred eighty-six thousand, five hundred thirty-one".