Isnt it unusual that when you sum the digits of 13 ² (169) it makes 16, when you do that again it makes 7,
And so, when you do that for 7 ² (49) it makes 13.
If summed up digits of number makes 4 or 7, it does not alter nevertheless you change the number. (4 ² makes 16, 16 ² makes 256 etc.).
Pretty unusual, huh?