689 has 4 divisors (see below), whose sum is σ = 756.
Its totient is φ = 624.
The previous prime is 683. The next prime is 691. The reversal of 689 is 986.
Subtracting from 689 its sum of digits (23), we obtain a palindrome (666).
It can be divided in two parts, 68 and 9, that added together give a palindrome (77).
689 is nontrivially palindromic in base 14.
689 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 289 + 400 = 17^2 + 20^2
It is not a de Polignac number, because 689 - 24 = 673 is a prime.
689 is a strobogrammatic number because it is the same when read upside-down.
It is a Duffinian number.
689 is an undulating number in base 14.
It is a plaindrome in base 10 and base 11.
It is a nialpdrome in base 13.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (683) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14 + ... + 39.
It is an arithmetic number, because the mean of its divisors is an integer number (189).
It is an amenable number.
689 is a deficient number, since it is larger than the sum of its proper divisors (67).
689 is a wasteful number, since it uses less digits than its factorization.
689 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 66.
The product of its digits is 432, while the sum is 23.
The square root of 689 is about 26.2488094968.
The cubic root of 689 is about 8.8322849909.
The spelling of 689 in words is "six hundred eighty-nine", and thus it is an aban number and an oban number.