There's no specific word that means "the number with the most zeroes" (out of a specific set), and there's no "number with the most zeroes" in general.
octillion
it is in the millions
sextillion
A number followed by 27 zeros is an octillion. This number is called 9 octillion
it is infinite. the most zeros in a number that we know today would have to be a hundred zeros. that number is called a google.
it is in the millions
octillion
sextillion
nonevsextillionocteillion
Trillion
2*1020 this is called 200quintillion a quintillion is a number with 18 zeros a sextillion is a number with 21 zeros your number has 20 zeros therefore it is not quite a sextillion yet.
A number followed by 27 zeros is an octillion. This number is called 9 octillion
ten's of billions
One billion
a googol? Nope that is 1 followed by one hundred zeros. A googolplex is one followed by a googol zeros. There is no broadly accepted name for 1 followed by one million zeros.