685871 has 4 divisors (see below), whose sum is σ = 700512. Its totient is φ = 671232.

The previous prime is 685859. The next prime is 685907. The reversal of 685871 is 178586.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 178586 = 2 ⋅89293.

It is a cyclic number.

It is not a de Polignac number, because 685871 - 2¹⁸ = 423727 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (685271) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7250 + ... + 7343.

It is an arithmetic number, because the mean of its divisors is an integer number (175128).

2⁶⁸⁵⁸⁷¹ is an apocalyptic number.

685871 is a deficient number, since it is larger than the sum of its proper divisors (14641).

685871 is a wasteful number, since it uses less digits than its factorization.

685871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14640.

The product of its digits is 13440, while the sum is 35.

The square root of 685871 is about 828.1732910448. The cubic root of 685871 is about 88.1889449211.

The spelling of 685871 in words is "six hundred eighty-five thousand, eight hundred seventy-one".