It is a happy number.
2181 is nontrivially palindromic in base 14.
2181 is an esthetic number in base 13, because in such base its adjacent digits differ by 1.
It is a D-number.
It is an alternating number because its digits alternate between even and odd.
It is a Duffinian number.
2181 is an undulating number in base 14.
It is a Curzon number.
It is a nialpdrome in base 3, base 5, base 13 and base 16.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 2181.
It is an amenable number.
2181 is an equidigital number, since it uses as much as digits as its factorization.
2181 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 730.
The square root of 2181 is about 46.7011777153. The cubic root of 2181 is about 12.9683648940.
Adding to 2181 its product of digits (16), we get a cube (2197 = 133).
Adding to 2181 its reverse (1812), we get a palindrome (3993).
The spelling of 2181 in words is "two thousand, one hundred eighty-one".