Let's get this math done. We have 864 and we're going to multiply it by 73. This is the same as taking 864 and adding it to itself 73 times.
Step 1: 0 + 864 = 864
Step 2: 864 + 864 = 1728
Step 3: 1728 + 864 = 2592
Step 4: 2592 + 864 = 3456
Step 5: 3456 + 864 = 4320
Step 6: 4320 + 864 = 5184
Step 7: 5184 + 864 = 6048
Step 8: 6048 + 864 = 6912
Step 9: 6912 + 864 = 7776
Step 10: 7776 + 864 = 8640
Step 11: 8640 + 864 = 9504
Step 12: 9504 + 864 = 10368
Step 13: 10368 + 864 = 11232
Step 14: 11232 + 864 = 12096
Step 15: 12096 + 864 = 12960
Step 16: 12960 + 864 = 13824
Step 17: 13824 + 864 = 14688
Step 18: 14688 + 864 = 15552
Step 19: 15552 + 864 = 16416
Step 20: 16416 + 864 = 17280
Step 21: 17280 + 864 = 18144
Step 22: 18144 + 864 = 19008
Step 23: 19008 + 864 = 19872
Step 24: 19872 + 864 = 20736
Step 25: 20736 + 864 = 21600
Step 26: 21600 + 864 = 22464
Step 27: 22464 + 864 = 23328
Step 28: 23328 + 864 = 24192
Step 29: 24192 + 864 = 25056
Step 30: 25056 + 864 = 25920
Step 31: 25920 + 864 = 26784
Step 32: 26784 + 864 = 27648
Step 33: 27648 + 864 = 28512
Step 34: 28512 + 864 = 29376
Step 35: 29376 + 864 = 30240
Step 36: 30240 + 864 = 31104
Step 37: 31104 + 864 = 31968
Step 38: 31968 + 864 = 32832
Step 39: 32832 + 864 = 33696
Step 40: 33696 + 864 = 34560
Step 41: 34560 + 864 = 35424
Step 42: 35424 + 864 = 36288
Step 43: 36288 + 864 = 37152
Step 44: 37152 + 864 = 38016
Step 45: 38016 + 864 = 38880
Step 46: 38880 + 864 = 39744
Step 47: 39744 + 864 = 40608
Step 48: 40608 + 864 = 41472
Step 49: 41472 + 864 = 42336
Step 50: 42336 + 864 = 43200
Step 51: 43200 + 864 = 44064
Step 52: 44064 + 864 = 44928
Step 53: 44928 + 864 = 45792
Step 54: 45792 + 864 = 46656
Step 55: 46656 + 864 = 47520
Step 56: 47520 + 864 = 48384
Step 57: 48384 + 864 = 49248
Step 58: 49248 + 864 = 50112
Step 59: 50112 + 864 = 50976
Step 60: 50976 + 864 = 51840
Step 61: 51840 + 864 = 52704
Step 62: 52704 + 864 = 53568
Step 63: 53568 + 864 = 54432
Step 64: 54432 + 864 = 55296
Step 65: 55296 + 864 = 56160
Step 66: 56160 + 864 = 57024
Step 67: 57024 + 864 = 57888
Step 68: 57888 + 864 = 58752
Step 69: 58752 + 864 = 59616
Step 70: 59616 + 864 = 60480
Step 71: 60480 + 864 = 61344
Step 72: 61344 + 864 = 62208
Step 73: 62208 + 864 = 63072

So, 864*73 = 63072