According to a reservation tracking spreadsheet on the Cybertruck Owners Club forum, the current tally of Tesla Cybertruck "pre-order reservations" exceeds 522,000. The forum states that "this is as calculated by this ongoing Cybertruck reservations tracking spreadsheet with actual order numbers inputted."
We have no way of knowing the actual number for sure since Tesla has never publicized an official Cybertruck reservation number. However, CEO Elon Musk was tweeting out numbers not long after the electric pickup truck was unveiled.
Based on Musk's last tweet with an assumed Cybertruck reservation number, Tesla had received some 250,000. That was back on November 26, 2019.