expr = Rationalize[{(2.5 + 1.5 Cos[v]) Cos[v/2], (2.5 + 1.5 Cos[v]) Sin[v/2], 1.5 Sin[v]}]

ArcLength[expr, {v, 0, 2*Pi}]/Pi

expr = Rationalize[{(2.5 + 1.5 Cos[v]) Cos[v/2], (2.5 + 1.5 Cos[v]) Sin[v/2], 1.5 Sin[v]}]
e1 = FullSimplify[#.# &@(D[#, v] & /@ expr), v > 0]

int = Integrate[Sqrt[e1], v];

Subtract @@ (int /. {{v -> 1.5}, {v -> 0.}})

In[11]:= ArcLength[expr, {v, 0, 1.5}]

Out[11]= 3.46249

In[12]:= ArcLength[expr, {v, 0., 2 Pi}]

Out[12]= 12.5426

In[13]:= NIntegrate[Sqrt[e1], {v, 0, 2 Pi}]

Out[13]= 12.5426

p1 = ParametricPlot3D[{2.5 Cos[u] + (1.5 Cos[v]*Cos[u]),
    2.5 Sin[u] + (1.5 Cos[v]*Sin[u]), 1.5 Sin[v]}, {v, 0, 2 Pi}, {u,
    0, 2 Pi}];
p2 = ParametricPlot3D[{(2.5 + 1.5 Cos[v]) Cos[
      v/2], (2.5 + 1.5 Cos[v]) Sin[v/2], 1.5 Sin[v]}, {v, 0, 2*Pi}];
Show[p1, p2]

boxed[x_String] := "\!\(\*StyleBox[" <> x <> ",\"Section\"]\)";

boxed["test"]

Style["test", "Section"]

"Test \!\(\*
StyleBox[\"italic\",\nFontSlant->\"Italic\"]\) and \!\(\*
StyleBox[\"underlined\",\nFontVariations->{\"Underline\"->True}]\)"

OverscriptBox[
    RowBox[{
       SuperscriptBox["x", "2"], "+",
       SuperscriptBox["y", "2"]}], "_"] // DisplayForm

OverscriptBox["x", "\[LongDash]"] // DisplayForm

OverscriptBox["x", "\[HorizontalLine]"] // DisplayForm

http://reference.wolfram.com/language/tutorial/GlobalSystemInformation.html

tutorial/GlobalSystemInformation