What does the 57 on a ketchup bottle mean?

"Heinz 57" is a synecdoche of the historical advertising slogan "57 Varieties of Pickles" by the H. J. Heinz Company (or where all John Kerry's money comes from).

It means 57 varieties, manufactured by Heinz, the maker of the ketchup on which the number 57 appears.

This is how it started - While riding a train in New York City in 1896, Henry Heinz saw a sign advertising 21 styles of shoes, which he thought was clever. Although Heinz was manufacturing more than 60 products at the time, Henry thought 57 was a lucky number. So, he began using the slogan "57 Varieties" in all his advertising.

Its an accidental marketing ploy that went well. ;-)

It's pretty common knowledge that the number represents the variety of products Heinz has; although, it is a little known fact that in the beginning, Henry Heinz simply used 57 because he thought it was a lucky number. Since then, the slogan '57 varieties' has stuck.

Heinz, the makers, used to produce 57 varieties of foodstuffs.