Revelation 13:18
15 The second beast was empowered to give life to the image of the first beast so that it could speak, and could cause all those who did not worship the image of the beast to be killed. 16 He also caused everyone (small and great, rich and poor, free and slave) to obtain a mark on their right hand or on their forehead. 17 Thus no one was allowed to buy or sell things unless he bore the mark of the beast—that is, his name or his number. 18 This calls for wisdom: Let the one who has insight calculate the beast’s number, for it is man’s number, and his number is 666.
Testament of Solomon 29
28 I then said to him, 'Bring me your child, who, as you claim, is in the Red Sea.' But he replied, 'I will not bring him to you. However, another demon called Ephippas will be compelled to bring him up from the deep to me.' I then inquired, 'Why is your son in the depth of the sea, and what is his name?' He answered, 'Do not ask me, for you cannot learn it from me. Nonetheless, he will come at your command and reveal everything openly.' 29 I said to him, 'Tell me by what angel you are thwarted.' And he replied, 'By the holy and precious name of the Almighty God, called by the Hebrews by a row of numbers, totaling 644, and by the Greeks, it is Emmanuel. If one of the Romans adjures me by the mighty name of the power Eleéth, I vanish at once.'
Notes and References
"... quite apart from the question of date, the very different content of these Solomonic texts indicates that they cannot be demonstrated to be more influential on the Apocalypse at Revelation 13:18 than the material from Kings (and Chronicles) discussed above. The most pertinent material, perhaps, might be the traditions found in the Testament of Solomon, but there is no positive mention of Solomon – as an exorcist or otherwise – in Revelation. Most telling of all, on the matter of distinctive content, is that none of these positive texts about Solomon mention 666. Third, it must be recalled that the kind of echoing or metaleptic activity posited here between Solomon and 666 in Revelation 13:18 generates or activates connections between the texts in question but does not require one-to-one correspondence in every detail. And so, fourth and finally, the relationship between 666 and Solomon need not and should not be construed as inflexible, let alone be misunderstood as one of complete identity or total identicalness ..."
Bodner, Keith and Brent A. Strawn Solomon and 666 (Revelation 13:18) (pp. 299-312) New Testament Studies, No. 66, 2020