Answer:
Zero
Step-by-step explanation:
A number divisible by 2 must be positive. Example: 2, 4, 6, 8
A number divisible by 5 must have either 5 or 0 in the ones place. Example: 15, 200, 3985, 4500
A number divisible by 9 must have numbers that add up to one of the multiples from nine. Example: 279 (2+7+9=18), 612 (6+1+2=9)
The digit that all numbers have in common is zero. Zero is considered positive, is one the numbers required for 5, and, with other numbers, can be divisible by 9.
