What is the largest fathomable number in the universe? According to Jude it's 161. As in, "Dad how fast can a dragster go? Can it go 161 miles per hour?" Or "Aww, we're never going to get there. It's like 161 miles away." Or "I want 161 bouncy houses."
For the littler Greyson, the biggest possible number is 61. As in, "Mom I see 61 cows," and "Jingle bells, jingle bells, jingle 61 bells all the way!"