Grandpa says : " Bit of a stretch but--
2.72 = 1000 x 10000
Is he crazy or genius?
2.72
e = 2.718281828... ~ 2.72
1000 x 10000
M = 1000 and C= 100 in Roman numerals so $c^2 = 10000$
Relatively speaking I think Grandpa is a genius
$E = mc^2$