289

289 = 17².

289 is the largest 3-digit square with increasing digits.

289 has a representation as a sum of two squares: 289 = 8² + 15².

289 is the hypotenuse of a primitive Pythagorean triple: 289² = 161² + 240².

289 is a centered octagonal number.

The Ford Mustang 289 was a high-performance version of the car in the 1960s.

Source: Number Gossip