2181

2181 = 3 x 727. It is an odd number with two distinct palindromic prime factors (A046404).

2181, 2182, and 2183 are each the product of two primes (semiprimes) (A056809).

The sum of 2181 and the 2181st prime (19,231) produces a palindrome (A115884): 2181 + 91231 = 21412.

2181 is the maximum length of a non-crossing path on a 34 x 34 square lattice (A049486).

2181 has the representation 2181 = 3⁷ - 1.

2181 is a divisor of 46¹¹ - 1.

Source: On-Line Encyclopedia of Integer Sequences