Across: A: A prime number.
E: A palindrome.
F: A multiple of C down.
G: The addition of E across, F across and C down.
K: All digits of K across are the same.
I: The digit sum of E across.
J: A square number.
K: The digit sum of I across multiplied by D down.

Down: A: A square number.
B: A multiple of J down.
C: The product of I across and a multiple of A down.
D: A palindrome.
H: A prime number.
J: A prime number.