I went into the article expecting it be full of usual banal platitudes, but it's a cute little list of random stuff. I was also pleasantly surprised to see 'ek number' on the list though.
Ek number was commonly used in my childhood days in Mumbai and it means "First class" or "Classic". Typical uses: ek number joke, ek number daaru (daaru = alcohol, liquor), ek number maal (First class, good looking, hot girl), ek number vada pav (classic food dish) etc.
The closest I can think is ek-dam but a person would rarely say that in response to a joke.
Other replies say it's a common phrase in Maharashtra too, TIL.