Sure thing, let's get straight to it. We start with 573 and we're going to multiply it by 21, which means adding 573 to itself 21 times.
Step 1: 0 + 573 = 573
Step 2: 573 + 573 = 1146
Step 3: 1146 + 573 = 1719
Step 4: 1719 + 573 = 2292
Step 5: 2292 + 573 = 2865
Step 6: 2865 + 573 = 3438
Step 7: 3438 + 573 = 4011
Step 8: 4011 + 573 = 4584
Step 9: 4584 + 573 = 5157
Step 10: 5157 + 573 = 5730
Step 11: 5730 + 573 = 6303
Step 12: 6303 + 573 = 6876
Step 13: 6876 + 573 = 7449
Step 14: 7449 + 573 = 8022
Step 15: 8022 + 573 = 8595
Step 16: 8595 + 573 = 9168
Step 17: 9168 + 573 = 9741
Step 18: 9741 + 573 = 10314
Step 19: 10314 + 573 = 10887
Step 20: 10887 + 573 = 11460
Step 21: 11460 + 573 = 12033

So, 573*21 = 12033