Let's roll up our sleeves and solve this. We have 573 and we're going to multiply it by 91, essentially adding 573 to itself 91 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
Step 22: 12033 + 573 = 12606
Step 23: 12606 + 573 = 13179
Step 24: 13179 + 573 = 13752
Step 25: 13752 + 573 = 14325
Step 26: 14325 + 573 = 14898
Step 27: 14898 + 573 = 15471
Step 28: 15471 + 573 = 16044
Step 29: 16044 + 573 = 16617
Step 30: 16617 + 573 = 17190
Step 31: 17190 + 573 = 17763
Step 32: 17763 + 573 = 18336
Step 33: 18336 + 573 = 18909
Step 34: 18909 + 573 = 19482
Step 35: 19482 + 573 = 20055
Step 36: 20055 + 573 = 20628
Step 37: 20628 + 573 = 21201
Step 38: 21201 + 573 = 21774
Step 39: 21774 + 573 = 22347
Step 40: 22347 + 573 = 22920
Step 41: 22920 + 573 = 23493
Step 42: 23493 + 573 = 24066
Step 43: 24066 + 573 = 24639
Step 44: 24639 + 573 = 25212
Step 45: 25212 + 573 = 25785
Step 46: 25785 + 573 = 26358
Step 47: 26358 + 573 = 26931
Step 48: 26931 + 573 = 27504
Step 49: 27504 + 573 = 28077
Step 50: 28077 + 573 = 28650
Step 51: 28650 + 573 = 29223
Step 52: 29223 + 573 = 29796
Step 53: 29796 + 573 = 30369
Step 54: 30369 + 573 = 30942
Step 55: 30942 + 573 = 31515
Step 56: 31515 + 573 = 32088
Step 57: 32088 + 573 = 32661
Step 58: 32661 + 573 = 33234
Step 59: 33234 + 573 = 33807
Step 60: 33807 + 573 = 34380
Step 61: 34380 + 573 = 34953
Step 62: 34953 + 573 = 35526
Step 63: 35526 + 573 = 36099
Step 64: 36099 + 573 = 36672
Step 65: 36672 + 573 = 37245
Step 66: 37245 + 573 = 37818
Step 67: 37818 + 573 = 38391
Step 68: 38391 + 573 = 38964
Step 69: 38964 + 573 = 39537
Step 70: 39537 + 573 = 40110
Step 71: 40110 + 573 = 40683
Step 72: 40683 + 573 = 41256
Step 73: 41256 + 573 = 41829
Step 74: 41829 + 573 = 42402
Step 75: 42402 + 573 = 42975
Step 76: 42975 + 573 = 43548
Step 77: 43548 + 573 = 44121
Step 78: 44121 + 573 = 44694
Step 79: 44694 + 573 = 45267
Step 80: 45267 + 573 = 45840
Step 81: 45840 + 573 = 46413
Step 82: 46413 + 573 = 46986
Step 83: 46986 + 573 = 47559
Step 84: 47559 + 573 = 48132
Step 85: 48132 + 573 = 48705
Step 86: 48705 + 573 = 49278
Step 87: 49278 + 573 = 49851
Step 88: 49851 + 573 = 50424
Step 89: 50424 + 573 = 50997
Step 90: 50997 + 573 = 51570
Step 91: 51570 + 573 = 52143

So, 573*91 = 52143