The reason lies with the way in which the operation "plus" is defined and the way in which numbers are represented.
-123454
203
Protactinium 234 is a decay product of thorium 234; the nuclear reaction is: 23490Th---------------23491Pa + beta rays (e-)
468
468
89+234=923
234 + 231 = 465
1932 + 234 = 2,166
234 + 646 = 880
234 + 3747943 = 3748177
234 + 455 = 689
234 + 12 = 246