Alright, let's solve this math problem step by step. First, we have the number 63. 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 63 and add it to itself 21 times.
Step 1: 0 + 63 = 63
Step 2: 63 + 63 = 126
Step 3: 126 + 63 = 189
Step 4: 189 + 63 = 252
Step 5: 252 + 63 = 315
Step 6: 315 + 63 = 378
Step 7: 378 + 63 = 441
Step 8: 441 + 63 = 504
Step 9: 504 + 63 = 567
Step 10: 567 + 63 = 630
Step 11: 630 + 63 = 693
Step 12: 693 + 63 = 756
Step 13: 756 + 63 = 819
Step 14: 819 + 63 = 882
Step 15: 882 + 63 = 945
Step 16: 945 + 63 = 1008
Step 17: 1008 + 63 = 1071
Step 18: 1071 + 63 = 1134
Step 19: 1134 + 63 = 1197
Step 20: 1197 + 63 = 1260
Step 21: 1260 + 63 = 1323

So, 63*21 = 1323