213685 has 4 divisors (see below), whose sum is σ = 256428. Its totient is φ = 170944.

The previous prime is 213659. The next prime is 213713. The reversal of 213685 is 586312.

It is a happy number.

213685 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 116964 + 96721 = 342^2 + 311^2 .

It is a cyclic number.

It is not a de Polignac number, because 213685 - 2⁷ = 213557 is a prime.

It is a super-2 number, since 2×213685² = 91322558450, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

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, 21364 + ... + 21373.

It is an arithmetic number, because the mean of its divisors is an integer number (64107).

2²¹³⁶⁸⁵ is an apocalyptic number.

It is an amenable number.

213685 is a deficient number, since it is larger than the sum of its proper divisors (42743).

213685 is an equidigital number, since it uses as much as digits as its factorization.

213685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42742.

The product of its digits is 1440, while the sum is 25.

The square root of 213685 is about 462.2607489286. The cubic root of 213685 is about 59.7848777771.

Adding to 213685 its reverse (586312), we get a palindrome (799997).

It can be divided in two parts, 213 and 685, that added together give a palindrome (898).

The spelling of 213685 in words is "two hundred thirteen thousand, six hundred eighty-five".