XXV

(the mandatory birthday post)

A quarter of a century, they say. Halfway to fifty, they say. This is not good enough. If you had said something like...

[25] is a square number, being 5² = 5 × 5, and it is also the sum of two squares, 3² + 4², often used in demonstrations of the Pythagorean theorem. It is the smallest square that is also a sum of two squares. 25 is a centered octagonal number and an automorphic number.

It is the first/smallest base 10 Friedman number as it can be expressed by its own numbers: 5².

It is also a Cullen number. 25 is the smallest pseudoprime satisfying the congruence 7ⁿ = 7 mod n. It is also a Somer pseudoprime based on 6.

Within base 10 one can readily test for divisibility by 25 by seeing if the last two digits of the number match 25, 50, 75 or 00. (Wikipedia)

Then I would have been impressed.

I just found out that this means that I am now eligble to run for President of the United States (if I was a citizen, that is). How about that?