21 LOR's??
what a slacker !

i used 3. of which 1 was internal.
1 was was one from an FO when i was a Capt.
1 was from a Capt when i was from an FO
1 was from a Check Airman that i had handful of check rides and line checks from.

good luck to the hopeful going thru the process, and hope to see you on the line.