WASHINGTON — Michelle Obama turned 50 on Friday and promptly showed off her AARP card.

“Excited to join Barack in the 50+ club today … check out my @AARP card!” the first lady told her more than 600,000 Twitter followers in a post that included a photo of her smiling and holding up the red-and-white membership card that bears her name.

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President Obama turned 50 in 2011.

Other than the Twitter pic, the first lady spent her big day out of sight, with no public appearances after back-to-back events at the White House earlier this week.

It was probably a good way to spend the birthday, resting up for a big birthday dance party the president has been planning for Saturday night at the White House.