On the multiplicative properties modulo m of numbers with missing digits
Nikolay Moshchevitin, Il'ya Dmitrievich Shkredov · Mathematical Notes · 2007
We obtain upper bounds for character sums modulo a composite number over sets of numbers with missing digits in a number system. We derive results on the solvability of congruences of the form x 1 ⋯ x t ≡ λ (mod m) in the numbers with missing digits and also asymptotic formulas for the number of solutions.