Why was the alif omitted from "Bismillāh" in this verse, and is there a connection to the number 19?

Al-Qurtubi, in his Tafsir, discussed that the omission of the alif from "Bismil-lah" (بسم الله) is due to its frequent usage, unlike "Iqra bismi Rabbika" (اقرأ باسم ربك) where it was not omitted because of its infrequent usage. There is disagreement regarding its omission with "Ar-Rahman" (الرحمن) and "Al-Qahir" (القاهر); Al-Kisa'i and Sa'id al-Akhfash held the view that it should be omitted, while Yahya ibn Waththab believed that it is only omitted with "Bismil-lah" due to its extensive usage. The mentioned number has no relation to the omission of the alif.