The terms are "Cardinal" and "Ordinal" and "Distributive". One, two, three, etc. are "Cardinal Numbers." First, second, third, etc. are "Ordinal Numbers" (which tell Order). "Distributive Numbers" tell how many of each like Singly,Doubly,Triply and Single,Double,Triple.
We often get the various -nary terms like binary, ternary, and quaternary from Latin distributive numbers (bini, terni, quaterni, quini, seni, etc.), with the exception of unary which comes from their cardinal number one (unus) as opposed to their distributive number one (singuli, which is where singular, single, singularity, etc. come from). Words like primary, secondary, and tertiary usually come from their ordinal numbers (primus, secundus, tertius, quartus, quintus, etc.).
The term you are probably looking for is the small hours.
Collins defines this term as "the early hours of the morning, after midnight and before dawn."
Best Answer
It is a colon. The typographic symbol - :
Its usage in denoting time is not universal, however. Many countries use a period (full stop) in its place. (14.23 for 2:23 PM).
To my knowledge there is not a special term to designate a colon separating hours:minutes.