256686 has 16 divisors (see below), whose sum is σ = 518400. Its totient is φ = 84728.

The previous prime is 256661. The next prime is 256687. The reversal of 256686 is 686652.

256686 is a nontrivial binomial coefficient, being equal to C(717, 2).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256687) by changing a digit.

256686 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 7 ways as a sum of consecutive naturals, for example, 955 + ... + 1193.

It is an arithmetic number, because the mean of its divisors is an integer number (32400).

2²⁵⁶⁶⁸⁶ is an apocalyptic number.

256686 is the 716-th triangular number.

256686 is an abundant number, since it is smaller than the sum of its proper divisors (261714).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

256686 is a wasteful number, since it uses less digits than its factorization.

256686 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 423.

The product of its digits is 17280, while the sum is 33.

The square root of 256686 is about 506.6418853589. The cubic root of 256686 is about 63.5527080099.

It can be divided in two parts, 256 and 686, that multiplied together give a cube (175616 = 56³).

The spelling of 256686 in words is "two hundred fifty-six thousand, six hundred eighty-six".