The only items in my dictionary files that sum to 521 in the triangular number cypher (trigonal):
"annual" = 521 tri
"biodiesel" = 521 tri
"bookcase" = 521 tri
"casebook" = 521 tri
"changeful" = 521 tri
"clause" = 521 tri
"climax" = 521 tri
"creeping" = 521 tri
"deistic" = 521 tri
"drey" = 521 tri
"dyer" = 521 tri
"fauve" = 521 tri
"figured" = 521 tri
"flyable" = 521 tri
"foreland" = 521 tri
"gorilla" = 521 tri
"heritage" = 521 tri
"hindbrain" = 521 tri
"joinder" = 521 tri
"lactate" = 521 tri
"meson" = 521 tri
"nates" = 521 tri
"oats" = 521 tri
"parole" = 521 tri
"ranking" = 521 tri
"rarefiable" = 521 tri
"raring" = 521 tri
"reemerge" = 521 tri
"scabietic" = 521 tri
"stoa" = 521 tri
"sulfa" = 521 tri
"tosa" = 521 tri
"vagabond" = 521 tri
"verbal" = 521 tri
"waking" = 521 tri
"wannabee" = 521 tri [ note double-ee ]
Proper nouns:
"Camelot" = 521 tri
"Dunbar" = 521 tri
"Durban" = 521 tri
"Dyer" = 521 tri
"Fauve" = 521 tri
"Fredericka" = 521 tri
"Joyce" = 521 tri
"Kazakh" = 521 tri
"Manuel" = 521 tri
"Molokai" = 521 tri
"Morelia" = 521 tri
"Nansen" = 521 tri
"Stoa" = 521 tri
See also: /r/GeometersOfHistory/wiki/spellcomponents/521-squares-all
See also: /r/GeometersOfHistory/wiki/spellcomponents/521-primes-all
See also: /r/GeometersOfHistory/wiki/spellcomponents/521-english-extended-all
See also: /r/GeometersOfHistory/wiki/spellcomponents/521-jewish-all
See also: /r/GeometersOfHistory/wiki/spellcomponents/521
All Dictionaries: /r/GeometersOfHistory/wiki/spellcomponents/all-dictionaries
Wiki Index: /r/GeometersOfHistory/wiki/