The digits briefly appeared on her Twitter feed before being deleted.
But some of the more eagle-eyed among her eight million followers caught the inadvertent post and called the number up.
They found it belonged to Duncan Wolfe, who worked at the White House as videographer and "creative digital strategist" under the Obamas and who is now a Chicago filmmaker and director.
The tweet was a simple mistake, the team working for Michelle Obama and former president Barack Obama said, and not any sign of a hacked account.
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