Alright, let's solve this math problem step by step. First, we have the number 491. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 21. So, we're going to take the number 491 and add it to itself 21 times.
Step 1: 0 + 491 = 491
Step 2: 491 + 491 = 982
Step 3: 982 + 491 = 1473
Step 4: 1473 + 491 = 1964
Step 5: 1964 + 491 = 2455
Step 6: 2455 + 491 = 2946
Step 7: 2946 + 491 = 3437
Step 8: 3437 + 491 = 3928
Step 9: 3928 + 491 = 4419
Step 10: 4419 + 491 = 4910
Step 11: 4910 + 491 = 5401
Step 12: 5401 + 491 = 5892
Step 13: 5892 + 491 = 6383
Step 14: 6383 + 491 = 6874
Step 15: 6874 + 491 = 7365
Step 16: 7365 + 491 = 7856
Step 17: 7856 + 491 = 8347
Step 18: 8347 + 491 = 8838
Step 19: 8838 + 491 = 9329
Step 20: 9329 + 491 = 9820
Step 21: 9820 + 491 = 10311

So, 491*21 = 10311