The Collaborative International Dictionary of English v.0.48:

Prodigiousness \Pro*di"gious*ness\, n.
   The quality or state of being prodigious; the state of having
   qualities that excite wonder or astonishment; enormousness;
   vastness.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "prodigiousness":
   ampleness, amplitude, awesomeness, beguilingness, boundlessness,
   bulk, enchantingness, enormity, enormousness, enticingness,
   exceptionality, expanse, extraordinariness, fabulousness,
   fascination, formidableness, fullness, gigantism, glamorousness,
   grandeur, grandness, great scope, greatness, hugeness, immensity,
   impossibility, inconceivability, incredibility, increditability,
   infinity, intensity, largeness, magnitude, marvelousness, might,
   mightiness, miraculousness, monstrosity, monstrousness, muchness,
   mysteriousness, mystery, mythicalness, numinousness,
   phenomenalness, plenitude, power, rareness, rarity, remarkableness,
   seductiveness, strength, stupendousness, tremendousness,
   uncommonness, uniqueness, unordinariness, unusualness,
   unwontedness, vastness, wonderfulness, wondrousness