5545

5545 = 5 x 1109.

5545 is a member of the Fibonacci-type sequence starting with 1 and 5 (A022095).

5545 uses only the digits 1 and 2 in base 4 (1112221) and base 7 (22111).

5545 is a concentric dodecagonal number (A195143).

5545 has two representations as a sum of two squares: 5545 = 19² + 72² = 28² + 69².

5545 is the hypotenuse of two primitive Pythagorean triples: 5545² = 2736² + 4823² = 3864² + 3977².

Source: What's Special About This Number?