An extravagant number (also known as a wasteful number) is a natural number that has fewer digits than the number of digits in its prime factorization (including exponents). For example, in base-10 arithmetic 4 = 2², 6 = 2×3, 8 = 2³, and 9 = 3² are extravagant numbers.
Extravagant numbers can be defined in any base. There are infinitely many extravagant numbers, no matter what base is used.
R.G.E. Pinch (1998), Economical Numbers
Chris Caldwell, The Prime Glossary: extravagant number at The Prime Pages.