They are 'square' numbers. 6x6=36, 9x9=81 and 5x5=25. Some other square numbers are 64, 4, 9, 100 & 121
They are 25, 36, 49, 64, and 81 .
25 36 49 64 81
They are all perfect squares.
4, 9, 16, 25, 36, 49, 64, 81
1, 4, 9, 16, 25, 36, 49, 64, 81, 100
1, 4, 9, 16, 25, 36, 49, 64, 81, 100
1, 4, 9, 16, 25, 36, 49, 64, 81
1491625364964811001, 4, 9, 16, 25, 36, 49, 64, 81, and 100
0, 1, 4, 9, 16, 25, 36, 49, 64, 81
1, 4, 9, 16, 25, 36, 49, 64, 81, 100
1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144
4,9,16,25,36,49,64,81,100,121