666 has no name but has a number. He is a devil who looks like a tall man(7'0). He has short red hair, beard, pale red skin, red eyes. 666 has a devilish tail and black horns. His body is muscular.
His age is not known, but it is assumed that he is a long-lived entity.
666 has different devilish powers. 
He also uses his devil wings on various occasions.
In conversation, he is a funny man who jokes. But he also likes to speak sarcastically. Sometimes he is serious and cold.
He also loves pranks.