However, it is the only composite number n for which is false. It is also a Motzkin number. In bases 6 and 12, 4 is a 1- automorphic number. In addition, 2 + 2 = 2 Ã 2 = 2 2 = 4. Continuing the pattern in Knuth's up-arrow notation, , and so on, for any number of up arrows.he next highly composite number is 6. Four is the second square number, the second centered triangular number. Of course, there are four sides to the square as well as four vertices, analogous to the four corners of a room.