Which of the following number is NOT divisible by 18?

Concept: A number is divisible by 18 if and only if it is divisible by both 2 and 9. Divisibility by 2 requires the number to be even (last digit 0, 2, 4, 6, or 8); divisibility by 9 requires the sum of its digits to be a multiple of 9.

Application — check each option against both conditions:

1. 50436: last digit 6 (even); digit sum 5+0+4+3+6 = 18 (multiple of 9) — divisible by 18.

2. 54036: last digit 6 (even); digit sum 5+4+0+3+6 = 18 (multiple of 9) — divisible by 18.

3. 65043: last digit 3 (odd) — fails the divisibility-by-2 condition, so it cannot be divisible by 18 regardless of its digit sum.

4. 34056: last digit 6 (even); digit sum 3+4+0+5+6 = 18 (multiple of 9) — divisible by 18.

Cross-check: three of the four numbers (50436, 54036, 34056) satisfy both the evenness and digit-sum conditions and are therefore divisible by 18; only one number fails the evenness condition, confirming which number is not divisible by 18.

∴ Required number = 65043