6623 = 37 x 179.
6623 has the property that the sum of its prime factors is equal to the product of its digits (A067173).
6623 is a centered heptagonal number (A069099).
6623 is a number n such that the nth and the (n + 1)th primes have the same sum of their digits squared (A109182).
6623 is a member of the Fibonacci-like sequence beginning with 12 and 67 (A091074).
6623 is a number that cannot be written as a sum of three squares.
Source: What's Special About This Number?