1849 = 432, a perfect square.
1849 is a centered octagonal number.
1849 is a perfect power in which neighboring digits are distinct.
Felix Klein (1849–1925) was born on April 25, 1849 (4/25/1849). Klein took particular delight in pointing out that each of the day (52), month (22), and year (432) is the square of a prime number.
Source: The MacTutor History of Mathematics Archive
Image: Portrait Gallery