1685 has 4 divisors (see below), whose sum is σ = 2028. Its totient is φ = 1344.

The previous prime is 1669. The next prime is 1693. The reversal of 1685 is 5861.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 529 + 1156 = 23^2 + 34^2 .

It is a cyclic number.

It is not a de Polignac number, because 1685 - 2⁴ = 1669 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 6.

It is a nialpdrome in base 12, base 14 and base 15.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164 + ... + 173.

It is an arithmetic number, because the mean of its divisors is an integer number (507).

It is an amenable number.

1685 is a deficient number, since it is larger than the sum of its proper divisors (343).

1685 is an equidigital number, since it uses as much as digits as its factorization.

1685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 342.

The product of its digits is 240, while the sum is 20.

The square root of 1685 is about 41.0487515035. The cubic root of 1685 is about 11.8996257209.

It can be divided in two parts, 16 and 85, that added together give a palindrome (101).

The spelling of 1685 in words is "one thousand, six hundred eighty-five".