NY Times Crossword
May 27, 2018
Andrew Chaikin
(Title shown below)

The three clues below have two things in common. The first is not too hard to see, but the second is not obvious at all.

AGE FOR DRINKING LEGALLY
GUNS IN A MILITARY SALUTE
SPOTS ON ALL SIDES OF A DIE

Not too hard to see answer:

21

Not obvious at all answer:

All three clues have exactly 21 letters.

Puzzle title: TWENTY-ONE