Had to look it up to make sure I'm using English right:
digit - The digits of the decimal number system are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9, and those in the hexadecimal number system are those in the decimal system along with A, B, C, D, E and F.
Letters count. Ultimately I'm looking to find the transaction hash that matches the beginning the best.