Using modern standard subtractive notation (i.e. IV = 4, IX = 9, XL = 40, XLIX = 49, XC = 90, etc.) there is something quite significant about the Roman number XXXVIII (38). What is it?
Significance may be in the eye of the beholder: there are probably some special properties of the Roman expression, e.g. the smallest number requiring seven symbols (if one requires the subtractive notation, or even without that limitation). Its square would be MCCCCXLIV -- I think CD for 400 is not generally allowed. Hardly cosmic significance, I opine.