A: a prime number.
D: A down / C down.
F: a prime number.
G: a square number.
H: add two to E down and multiply the result with the sum of the digits of D across to get H across.
A: see D across.
B: the reverse of A across.
C: the sum of C down's digits equals the first digit of D across.
E: a palindrome (a number that is equal to its reverse).