The sum of any two of these numbers is a perfect square:
7442 + 28658 = 1902
7442 + 148583 = 3952
7442 + 177458 = 4302
7442 + 763442 = 8782
28658 + 148583 = 4212
28658 + 177458 = 4542
28658 + 763442 = 8902
148583 + 177458 = 5712
148583 + 763442 = 9552
177458 + 763442 = 9702
Two other such sets:
{-15863902, 17798783, 21126338, 49064546, 82221218, 447422978}
{30823058, 63849842, 150187058, 352514183, 1727301842}
Whether there’s a set of six positive integers with this property is an open question.
(A.R. Thatcher, “Five Integers Which Sum in Pairs to Squares,” Mathematical Gazette 62:419 [March 1978], 25-29.)