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.

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.