686138 has 8 divisors (see below), whose sum is σ = 1048788. Its totient is φ = 336544.

The previous prime is 686131. The next prime is 686141. The reversal of 686138 is 831686.

Added to its reverse (831686) it gives a square (1517824 = 1232²).

686138 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 683929 + 2209 = 827^2 + 47^2 .

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

It is not an unprimeable number, because it can be changed into a prime (686131) by changing a digit.

686138 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 3 ways as a sum of consecutive naturals, for example, 3131 + ... + 3342.

2⁶⁸⁶¹³⁸ is an apocalyptic number.

686138 is a deficient number, since it is larger than the sum of its proper divisors (362650).

686138 is a wasteful number, since it uses less digits than its factorization.

686138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6528.

The product of its digits is 6912, while the sum is 32.

The square root of 686138 is about 828.3344735069. The cubic root of 686138 is about 88.2003870113.

Adding to 686138 its reverse (831686), we get a square (1517824 = 1232²).

The spelling of 686138 in words is "six hundred eighty-six thousand, one hundred thirty-eight".