A numberis called economical if the number of digits in its prime factorization (including exponents greater than 1) is not greater than the number of digits of

In practice, economical numbers are the union of equidigital and frugal numbers.

For example, and are both economical.

Some authors call the frugal numbers economical.

The numbers which are not economical are called wasteful.

The first economical numbers are 2, 3, 5, 7, 10, 11, 13, 14, 15, 16, 17, 19, 21, 23, 25, 27, 29, 31, 32, 35, 37, 41, 43, 47, 49, 53, 59, 61, 64 more terms

The smallest 3 × 3 magic square whose entries are consecutive economical numbers is

245 229 243 237 239 241 235 249 233

Below, the spiral pattern of economical numbers up to . See the page on prime numbers for an explanation and links to similar pictures.