I'll induce thread creep rather than start another OT thread for this one.

Any suggestions for an answer to the following enigma? It's a number, but has me stumped, since I never heard the nursery rhyme/prayer in question, and Google hasn't given me any usable leads.

An enumeration, this,
Found in doggerel, not so deep,
'Bout Apostles, of the twelve,
Blessing that 'pon which I sleep.