686506 has 4 divisors (see below), whose sum is σ = 1029762. Its totient is φ = 343252.

The previous prime is 686503. The next prime is 686513. The reversal of 686506 is 605686.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 605686 = 2 ⋅302843.

It can be written as a sum of positive squares in only one way, i.e., 410881 + 275625 = 641^2 + 525^2 .

It is a super-3 number, since 3×686506³ = 970631243338926648, which contains 333 as substring.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (686503) 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 as a sum of consecutive naturals, namely, 171625 + ... + 171628.

2⁶⁸⁶⁵⁰⁶ is an apocalyptic number.

686506 is a deficient number, since it is larger than the sum of its proper divisors (343256).

686506 is a wasteful number, since it uses less digits than its factorization.

686506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343255.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 686506 is about 828.5565762216. The cubic root of 686506 is about 88.2161525188.

The spelling of 686506 in words is "six hundred eighty-six thousand, five hundred six".