690 has 16 divisors (see below), whose sum is σ = 1728.
Its totient is φ = 176.
The previous prime is 683. The next prime is 691. The reversal of 690 is 96.
690 is nontrivially palindromic in base 16.
690 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a super-2 number, since 2×6902 = 952200, which contains 22 as substring.
It is a Smith number, since the sum of its digits (15) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.
It is a Harshad number since it is a multiple of its sum of digits (15).
It is an Ulam number.
It is an alternating number because its digits alternate between even and odd.
690 is an undulating number in base 16.
It is a Curzon number.
It is a plaindrome in base 11.
It is a nialpdrome in base 6, base 13 and base 15.
It is not an unprimeable number, because it can be changed into a prime (691) 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 7 ways as a sum of consecutive naturals, for example, 19 + ... + 41.
It is an arithmetic number, because the mean of its divisors is an integer number (108).
It is a practical number, because each smaller number is the sum of distinct divisors of 690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (864).
690 is an abundant number, since it is smaller than the sum of its proper divisors (1038).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
690 is a wasteful number, since it uses less digits than its factorization.
690 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 33.
The product of its (nonzero) digits is 54, while the sum is 15.
The square root of 690 is about 26.2678510731.
The cubic root of 690 is about 8.8365559224.
Subtracting from 690 its product of nonzero digits (54), we obtain a palindrome (636).
The spelling of 690 in words is "six hundred ninety", and thus it is an aban number and an oban number.