• 189 can be written using four 4's:
189 has 8 divisors (see below), whose sum is σ = 320. Its totient is φ = 108.
The previous prime is 181. The next prime is 191. The reversal of 189 is 981.
189 is nontrivially palindromic in base 2.
It is not a de Polignac number, because 189 - 23 = 181 is a prime.
It is an Ulam number.
It is an alternating number because its digits alternate between odd and even.
It is a Duffinian number.
It is a Curzon number.
189 is a lucky number.
It is a plaindrome in base 5, base 10, base 12, base 13 and base 16.
It is a nialpdrome in base 3, base 14 and base 15.
It is a congruent number.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24 + ... + 30.
It is an arithmetic number, because the mean of its divisors is an integer number (40).
189 is the 9-th heptagonal number.
It is an amenable number.
189 is a deficient number, since it is larger than the sum of its proper divisors (131).
189 is an equidigital number, since it uses as much as digits as its factorization.
189 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 16 (or 10 counting only the distinct ones).
The product of its digits is 72, while the sum is 18.
The square root of 189 is about 13.7477270849. The cubic root of 189 is about 5.7387935483.
Subtracting from 189 its sum of digits (18), we obtain a palindrome (171).
It can be divided in two parts, 18 and 9, that added together give a cube (27 = 33).
The spelling of 189 in words is "one hundred eighty-nine", and thus it is an aban number.
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