684865 has 4 divisors (see below), whose sum is σ = 821844. Its totient is φ = 547888.

The previous prime is 684857. The next prime is 684869. The reversal of 684865 is 568486.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 568486 = 2 ⋅284243.

It can be written as a sum of positive squares in 2 ways, for example, as 418609 + 266256 = 647^2 + 516^2 .

It is a cyclic number.

It is not a de Polignac number, because 684865 - 2³ = 684857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (684869) 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, 68482 + ... + 68491.

It is an arithmetic number, because the mean of its divisors is an integer number (205461).

2⁶⁸⁴⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

684865 is a deficient number, since it is larger than the sum of its proper divisors (136979).

684865 is a wasteful number, since it uses less digits than its factorization.

684865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136978.

The product of its digits is 46080, while the sum is 37.

The square root of 684865 is about 827.5657073611. The cubic root of 684865 is about 88.1458068336.

The spelling of 684865 in words is "six hundred eighty-four thousand, eight hundred sixty-five".