is a centreed octagonal number. is the smallest square number that can be written as a sum of 2 squares: 5^{2} = 4^{2} + 3^{2}
= 1 + 3 + 5 + 7 + 9 (sum of the first five odd numbers)
= (1^{2} + 2^{2})^{2 }= 13^{2} - 12^{2}
**25**^{2 }= 7^{2} + 24^{2} (Pythagorean triple)
4! + 1 = 25
25% = 1/4
When you add the digit 6 to 25 you obtain two squares: **6****25** = 25^{2}, and **25****6** = 16^{2}
We can readily test for divisibility by 25 by seeing if the last two digits of the number match 25, 50, 75 or 00.
It seems that **25** and 27 are the only case of a square and a cube separated by 2 (can you prove it?).
"The two greatest highway menaces are drivers under **25** going over 65 and drivers over 65 going under 25".
The **25th Hour** is a 2002 Spike Lee urban drama based on David Benioff's novel. |