144,000 is the number given in Revelations. It's not something unique to JW.
Correct you are. But as far as I know they are the only religion that has taken the verse, Revelation 7:4, and applied it to their belief. Which makes no sense because the verse refers to the sons of Israel which the JW's I've met clearly are not in the least bit Jewish. In addition, there are way more than 144,000 of them in the US alone so according to their beliefs, I wonder which of them would be entering heaven and which would be denied. It's a question they are hard pressed to answer.
In the southern town I'm from, I knew the head of the JW church there. He was a very wealthy man and made his money from those that honestly thought he was something special. He sure didn't live the life he preached, at least when he didn't have them around.