K-39 - The Challengers (for those who like classic surf music)
5:15 - The Who.
4′33″ - John Cage.
1984 - David Bowie (Very likely there are also other songs entitled 1984.)
Just the first four numbers: Lee Hi’s 1 2 3 4.
The Byrds, C.T.A.-102
*Pi *by Kate Bush off of Aerial.
Also “1,000,000”. Okay, not a letter-number combo, unless you add the band name.
(In which case, we might include “One” by U2).
1-2-3 - Len Barry
1234 - Feist
CMC fnord!
409 - Beach Boys
Ross Ryan - 606.
909 1 
Uh, not to be pedantic, but the OP, judging by the examples he gave, is looking for song titles with letter/number combinations — not songs with only letters or only numbers. A lot of the songs posted here don’t qualify.
“HCO 97658” by Kak, an obscure (but wonderful) psychedelic rock group from the late 60s. I assume that was at one point the catalog number of the record.
Too bad we don’t have any examples by U2, or UB40.
Van Halen’s “A.F.U.” on the album OU812.
YAY! I thought of one.
SWLABR wasn’t random. It stands for She Was Like A Bearded Rainbow. Nonsensical, yes, but not random.
And I would nominate Wings’ “1985” (or Nineteen Hundred and Eighty Five if you prefer) but it has numbers only.
Did the movie *THX1138 *have a theme song?
Or EMI by the Sex Pistols. They also had a song called Seventeen, but on the label I think it was written out as a word, not numerals.
What about 7 Teen by The Regents, or 7 and 7 is by Love, do they count?
I suppose Pennsylvania 6-5000 (Glenn Miller) wouldn’t count?
2112 by Rush.
25 or 6 to 4 by Chicago?