2

2 (two) is a positive integer following 1 and preceding 3. Its ordinal form is written "second" of 2nd.

Properties
2 is, and a &mdash; the only number with both of those properties. Since 10 is a multiple of 2, a number can be easily be tested for evenness by looking at the last decimal digit. Even numbers always end in 0, 2, 4, 6, or 8.

In googology
\(2 \underbrace{\uparrow\uparrow\ldots\uparrow\uparrow}_n 2 = 4\) for all \(n \geq 1\). BEAF arrays using 2 as a base tend to become degenerate and evaluate to 4: {2, 2 (1) 2} = {2, 2} =  = 4. For this reason, Bowers often coins googologisms based on the number 3, which do not become degenerate.