It is a happy number.
6543 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.
It is an alternating number because its digits alternate between even and odd.
It is a Duffinian number.
It is a straight-line number, since its digits are in arithmetic progression.
It is a plaindrome in base 14.
It is a nialpdrome in base 3, base 9 and base 10.
It is a zygodrome in base 2.
It is a congruent number.
26543 is an apocalyptic number.
6543 is a wasteful number, since it uses less digits than its factorization.
6543 is an evil number, because the sum of its binary digits is even.
The square root of 6543 is about 80.8888125763. Note that the first 4 decimals coincide. The cubic root of 6543 is about 18.7036186959.
Adding to 6543 its sum of digits (18), we get a 8-th power (6561 = 38).
Adding to 6543 its product of digits (360), we get a triangular number (6903 = T117).
Adding to 6543 its reverse (3456), we get a palindrome (9999).
The spelling of 6543 in words is "six thousand, five hundred forty-three".