Good evening.
21 – number of days in the 3 weeks (not including 10 Menachem Ov).
Gematriya of Akeh (one of HaShem’s names spelled with two hei’s).
gematriya of ??
21 Nisan – Shvi’i shel Pesach in Eretz Yisroel
Number of times we daven Shmone Esrei in a regular week – not including Musof of Shabbos