2.1 Divisibility by 2

Rule: The last digit (units digit) is 0, 2, 4, 6, or 8 (i.e., even). Reasoning: Any number can be written as 10 × (rest) + (last digit). Since 10 is divisible by 2, the whole number’s divisibility by 2 depends only on the last digit.

Example 1: Is 3,58,942 divisible by 2? Last digit = 2 (even) → Yes. Example 2: Is 71,235 divisible by 2? Last digit = 5 (odd) → No.

Example 3: Is 7,19,458 divisible by 2? Last digit = 8 (even) → Yes.

Example 4 (edge case — two rules meeting on one digit): Is 83,470 divisible by 2, by 5, and by 10 simultaneously? Last digit = 0. A last digit of 0 is even (satisfies the rule for 2), is also 0 (satisfies the rule for 5), and is the only digit value that can satisfy the rule for 10. So 83,470 is divisible by 2, 5, and 10 all at once — a useful reminder that “ends in 0” is the special case where the 2-rule and 5-rule overlap completely.