MathDB

4-digit numbers

Source: 2015 Cuba 2.4

September 20, 2024

number theoryDigits

Problem Statement

Let

A = \overline{abcd}

be a

4

-digit positive integer, such that

a\ge 7

and

a > b >c > d > 0

. Let us consider a positive integer

B = \overline{dcba}

. If all digits of

A+B

are odd, determine all possible values of

A

.

Back to Problems View on AoPS