Which of the following is a prime number?

Given data & approach

• Test each option for primality by trial division up to its square root.

Checks

221 = 13 × 17 ⇒ composite217 = 7 × 31 ⇒ composite223: not divisible by 2, 3 (2+2+3=7), 5, 7 (7×32=224), 11 (11×20=220), 13 (13×17=221) ⇒ prime253 = 11 × 23 ⇒ composite

Final Answer

223 is prime.