White House press secretary Sarah Huckabee Sanders quipped Thursday: "If I do say so, I don't think he looks a day over 35."
She added: "A little sucking up's probably never bad."
Trump's elder daughter and senior adviser Ivanka Trump wished her dad "your best year yet!!!" in a birthday tweet.
Trump's eldest son, Donald Trump Jr., also celebrated the occasion on social media.
On Instagram, he posted a screenshot of a Drudge Report headline declaring, "TRUMP'S BEST BIRTHDAY!" and citing the economy, North Korea, the World Cup and the jobless rate.
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