686657 has 4 divisors (see below), whose sum is σ = 688896. Its totient is φ = 684420.

The previous prime is 686639. The next prime is 686669. The reversal of 686657 is 756686.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 686657 - 2⁶ = 686593 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 686657.

It is not an unprimeable number, because it can be changed into a prime (686687) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 569 + ... + 1302.

It is an arithmetic number, because the mean of its divisors is an integer number (172224).

2⁶⁸⁶⁶⁵⁷ is an apocalyptic number.

It is an amenable number.

686657 is a deficient number, since it is larger than the sum of its proper divisors (2239).

686657 is a wasteful number, since it uses less digits than its factorization.

686657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2238.

The product of its digits is 60480, while the sum is 38.

The square root of 686657 is about 828.6476935345. The cubic root of 686657 is about 88.2226198876. Note that the first 3 decimals are identical.

It can be divided in two parts, 68 and 6657, that multiplied together give a triangular number (452676 = T₉₅₁).

The spelling of 686657 in words is "six hundred eighty-six thousand, six hundred fifty-seven".