What's the noun for hexadecimals? Here's the word you're looking for.
hexadecimal
(computing) A number system with base 16, using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F, useful in computing as a hexadecimal digit can represent four bits, half a standard byte.
(computing) A number expressed in the hexadecimal system.