31685 has 4 divisors (see below), whose sum is σ = 38028. Its totient is φ = 25344.

The previous prime is 31667. The next prime is 31687. The reversal of 31685 is 58613.

It is a Cunningham number, because it is equal to 178²+1.

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 11236 + 20449 = 106^2 + 143^2 .

It is a cyclic number.

It is not a de Polignac number, because 31685 - 2¹⁰ = 30661 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 31685.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31687) 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, 3164 + ... + 3173.

It is an arithmetic number, because the mean of its divisors is an integer number (9507).

2³¹⁶⁸⁵ is an apocalyptic number.

It is an amenable number.

31685 is a deficient number, since it is larger than the sum of its proper divisors (6343).

31685 is an equidigital number, since it uses as much as digits as its factorization.

31685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6342.

The product of its digits is 720, while the sum is 23.

The square root of 31685 is about 178.0028089666. The cubic root of 31685 is about 31.6435041454.

The spelling of 31685 in words is "thirty-one thousand, six hundred eighty-five".