An insight that came to me on Yom Kippur.
(it is spelled חסר)
What letter is missing in the sequence?
Because two represents divisiveness, and separation, while three represents re-unification and integration.
vol. 1 p. 20 , 44; vol. 2 p. 108; vol. 3 pp. 100, 210
Avos p. 119
Gevuros Hashem pp. 58, 98
(and many other places)
Hence, the word has no ב.
spelled this way its gimatriya is 13 - אחד
Of course, לולב צריך אגד:
The 1 - esrog - א
And the 3- lulav, hadasim, aravos -ג
Equal the daled minim - ד