Letters in a Number

units = {"one", "two", "three", "four", "five", "six", "seven",
   "eight", "nine"};
tens = {"ten", "twenty", "thirty", "forty", "fifty", "sixty",
   "seventy", "eighty", "ninety"};
teens = {"eleven", "twelve", "thirteen", "fourteen", "fifteen",
   "sixteen", "seventeen", "eighteen", "nineteen"};
ToWords[n_] := If[11 <= n <= 19, teens[[n - 10]],
  If[Mod[n, 10] == 0,
   tens[[n/10]],
   If[1 <= n <= 9, units[[n]],
    StringJoin[tens[[Floor[n/10]]], units[[Floor[n - 10 Floor[n/10]]]]]
    ]
   ]
  ];
graph = Table[i -> StringLength[ToWords[i]], {i, 99}];
GraphPlot[graph, DirectedEdges -> True, VertexLabeling -> True,
 ImageSize -> 1000, PlotStyle -> RGBColor[0.1, 0.2, 0.5]]