We will later learn that King Noah’s wicked priests later kidnapped the Lamanite daughters, and we can assume that they took one each. Since twenty-four of the Lamanite daughters were abducted, that becomes one evidence that King Noah had 24 priests (Mosiah 20:1–5).
Several other evidences support that conclusion, as I argue in my chapter "The Trial of Abinadi." For example, in Israel, the seventy members of the Sanhedrin sat in three rows, and seventy divided by three is twenty-three and a third. One of the rows had twenty-four and the other two rows had twenty-three. For the big cases, you had to have the full Sanhedrin, all seventy. For a minor case, or for a case tried outside of Jerusalem, you just had to have one row: twenty-three or twenty-four. So that number seems to me to be at least plausible.
John W. Welch, "The Trial of Abinadi," in The Legal Cases in the Book of Mormon (Provo, UT: BYU Press, 2008), 170–173.