'Twenty first' in the Bible

In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, [and continue] until the twenty-first day of the month at evening.

the twenty-first to Jachin, the twenty-second to Gamul,

the twenty-first to Hothir, his sons and his relatives, twelve;

On the twenty-first day of the seventh month (Oct 17, 520 b.c., the second year of Darius king of Persia), the word of the Lord came by the prophet Haggai, saying,