Alright, let's solve this math problem step by step. First, we have the number 644. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 61. So, we're going to take the number 644 and add it to itself 61 times.
Step 1: 0 + 644 = 644
Step 2: 644 + 644 = 1288
Step 3: 1288 + 644 = 1932
Step 4: 1932 + 644 = 2576
Step 5: 2576 + 644 = 3220
Step 6: 3220 + 644 = 3864
Step 7: 3864 + 644 = 4508
Step 8: 4508 + 644 = 5152
Step 9: 5152 + 644 = 5796
Step 10: 5796 + 644 = 6440
Step 11: 6440 + 644 = 7084
Step 12: 7084 + 644 = 7728
Step 13: 7728 + 644 = 8372
Step 14: 8372 + 644 = 9016
Step 15: 9016 + 644 = 9660
Step 16: 9660 + 644 = 10304
Step 17: 10304 + 644 = 10948
Step 18: 10948 + 644 = 11592
Step 19: 11592 + 644 = 12236
Step 20: 12236 + 644 = 12880
Step 21: 12880 + 644 = 13524
Step 22: 13524 + 644 = 14168
Step 23: 14168 + 644 = 14812
Step 24: 14812 + 644 = 15456
Step 25: 15456 + 644 = 16100
Step 26: 16100 + 644 = 16744
Step 27: 16744 + 644 = 17388
Step 28: 17388 + 644 = 18032
Step 29: 18032 + 644 = 18676
Step 30: 18676 + 644 = 19320
Step 31: 19320 + 644 = 19964
Step 32: 19964 + 644 = 20608
Step 33: 20608 + 644 = 21252
Step 34: 21252 + 644 = 21896
Step 35: 21896 + 644 = 22540
Step 36: 22540 + 644 = 23184
Step 37: 23184 + 644 = 23828
Step 38: 23828 + 644 = 24472
Step 39: 24472 + 644 = 25116
Step 40: 25116 + 644 = 25760
Step 41: 25760 + 644 = 26404
Step 42: 26404 + 644 = 27048
Step 43: 27048 + 644 = 27692
Step 44: 27692 + 644 = 28336
Step 45: 28336 + 644 = 28980
Step 46: 28980 + 644 = 29624
Step 47: 29624 + 644 = 30268
Step 48: 30268 + 644 = 30912
Step 49: 30912 + 644 = 31556
Step 50: 31556 + 644 = 32200
Step 51: 32200 + 644 = 32844
Step 52: 32844 + 644 = 33488
Step 53: 33488 + 644 = 34132
Step 54: 34132 + 644 = 34776
Step 55: 34776 + 644 = 35420
Step 56: 35420 + 644 = 36064
Step 57: 36064 + 644 = 36708
Step 58: 36708 + 644 = 37352
Step 59: 37352 + 644 = 37996
Step 60: 37996 + 644 = 38640
Step 61: 38640 + 644 = 39284

So, 644*61 = 39284