AMC 10 Step by Step
Log inSign up
2021 AMC Fall 10AProblem 5P1-10~2 minPrint
PrimesDivisibility & FactorsUse the answer choices (mod checks, size, form) to eliminate or selectSet up the equation/formula and compute; no special trick needed

The six-digit number 2‾ 0‾ 2‾ 1‾ 0‾ A‾\underline{2}\,\underline{0}\,\underline{2}\,\underline{1}\,\underline{0}\,\underline{A} is prime for only one digit A.A. What is A?A?

Log in to save your progress.

Similar problems

Problem © Mathematical Association of America (MAA), American Mathematics Competitions. Reproduced for non-commercial educational use. Solution and commentary are original to this site. Also appeared as 2021 12FA #4.