209689 has 4 divisors (see below), whose sum is σ = 210724. Its totient is φ = 208656.

The previous prime is 209687. The next prime is 209701. The reversal of 209689 is 986902.

209689 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, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 80089 + 129600 = 283^2 + 360^2 .

It is a cyclic number.

It is not a de Polignac number, because 209689 - 2¹ = 209687 is a prime.

It is a Duffinian number.

209689 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (209687) 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, 102 + ... + 655.

It is an arithmetic number, because the mean of its divisors is an integer number (52681).

2²⁰⁹⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

209689 is a deficient number, since it is larger than the sum of its proper divisors (1035).

209689 is an equidigital number, since it uses as much as digits as its factorization.

209689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1034.

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 209689 is about 457.9181149507. The cubic root of 209689 is about 59.4098628130.

It can be divided in two parts, 209 and 689, that added together give a palindrome (898).

The spelling of 209689 in words is "two hundred nine thousand, six hundred eighty-nine".