685821 has 8 divisors (see below), whose sum is σ = 946080. Its totient is φ = 441392.

The previous prime is 685819. The next prime is 685849. The reversal of 685821 is 128586.

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

It is a cyclic number.

It is not a de Polignac number, because 685821 - 2¹ = 685819 is a prime.

685821 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 685821.

It is not an unprimeable number, because it can be changed into a prime (685621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3855 + ... + 4028.

It is an arithmetic number, because the mean of its divisors is an integer number (118260).

2⁶⁸⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

685821 is a deficient number, since it is larger than the sum of its proper divisors (260259).

685821 is a wasteful number, since it uses less digits than its factorization.

685821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7915.

The product of its digits is 3840, while the sum is 30.

The square root of 685821 is about 828.1431035757. The cubic root of 685821 is about 88.1868018775.

The spelling of 685821 in words is "six hundred eighty-five thousand, eight hundred twenty-one".