It's not binary because all of the intermediate results shown during the videos are also valid numbers. It's actually an (upside down so as not to spoil it for anyone) ˙ǝuo ɟo uoıʇıppɐ ʇuǝsǝɹdǝɹ sʇop ǝɥʇ puɐ 'oʍʇ ʎq pǝıןdıʇןnɯ sʇuǝʇuoɔ ǝɥʇ ɥʇıʍ sısǝɥʇuǝɹɐd ʇuǝsǝɹdǝɹ sǝןɔɹıɔ ǝɹǝɥʍ uoıssǝɹdxǝ ɔıʇǝɯɥʇıɹ∀