Alright, let's solve this math problem step by step. First, we have the number 645. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 256. So, we're going to take the number 645 and add it to itself 256 times.
Step 1: 0 + 645 = 645
Step 2: 645 + 645 = 1290
Step 3: 1290 + 645 = 1935
Step 4: 1935 + 645 = 2580
Step 5: 2580 + 645 = 3225
Step 6: 3225 + 645 = 3870
Step 7: 3870 + 645 = 4515
Step 8: 4515 + 645 = 5160
Step 9: 5160 + 645 = 5805
Step 10: 5805 + 645 = 6450
Step 11: 6450 + 645 = 7095
Step 12: 7095 + 645 = 7740
Step 13: 7740 + 645 = 8385
Step 14: 8385 + 645 = 9030
Step 15: 9030 + 645 = 9675
Step 16: 9675 + 645 = 10320
Step 17: 10320 + 645 = 10965
Step 18: 10965 + 645 = 11610
Step 19: 11610 + 645 = 12255
Step 20: 12255 + 645 = 12900
Step 21: 12900 + 645 = 13545
Step 22: 13545 + 645 = 14190
Step 23: 14190 + 645 = 14835
Step 24: 14835 + 645 = 15480
Step 25: 15480 + 645 = 16125
Step 26: 16125 + 645 = 16770
Step 27: 16770 + 645 = 17415
Step 28: 17415 + 645 = 18060
Step 29: 18060 + 645 = 18705
Step 30: 18705 + 645 = 19350
Step 31: 19350 + 645 = 19995
Step 32: 19995 + 645 = 20640
Step 33: 20640 + 645 = 21285
Step 34: 21285 + 645 = 21930
Step 35: 21930 + 645 = 22575
Step 36: 22575 + 645 = 23220
Step 37: 23220 + 645 = 23865
Step 38: 23865 + 645 = 24510
Step 39: 24510 + 645 = 25155
Step 40: 25155 + 645 = 25800
Step 41: 25800 + 645 = 26445
Step 42: 26445 + 645 = 27090
Step 43: 27090 + 645 = 27735
Step 44: 27735 + 645 = 28380
Step 45: 28380 + 645 = 29025
Step 46: 29025 + 645 = 29670
Step 47: 29670 + 645 = 30315
Step 48: 30315 + 645 = 30960
Step 49: 30960 + 645 = 31605
Step 50: 31605 + 645 = 32250
Step 51: 32250 + 645 = 32895
Step 52: 32895 + 645 = 33540
Step 53: 33540 + 645 = 34185
Step 54: 34185 + 645 = 34830
Step 55: 34830 + 645 = 35475
Step 56: 35475 + 645 = 36120
Step 57: 36120 + 645 = 36765
Step 58: 36765 + 645 = 37410
Step 59: 37410 + 645 = 38055
Step 60: 38055 + 645 = 38700
Step 61: 38700 + 645 = 39345
Step 62: 39345 + 645 = 39990
Step 63: 39990 + 645 = 40635
Step 64: 40635 + 645 = 41280
Step 65: 41280 + 645 = 41925
Step 66: 41925 + 645 = 42570
Step 67: 42570 + 645 = 43215
Step 68: 43215 + 645 = 43860
Step 69: 43860 + 645 = 44505
Step 70: 44505 + 645 = 45150
Step 71: 45150 + 645 = 45795
Step 72: 45795 + 645 = 46440
Step 73: 46440 + 645 = 47085
Step 74: 47085 + 645 = 47730
Step 75: 47730 + 645 = 48375
Step 76: 48375 + 645 = 49020
Step 77: 49020 + 645 = 49665
Step 78: 49665 + 645 = 50310
Step 79: 50310 + 645 = 50955
Step 80: 50955 + 645 = 51600
Step 81: 51600 + 645 = 52245
Step 82: 52245 + 645 = 52890
Step 83: 52890 + 645 = 53535
Step 84: 53535 + 645 = 54180
Step 85: 54180 + 645 = 54825
Step 86: 54825 + 645 = 55470
Step 87: 55470 + 645 = 56115
Step 88: 56115 + 645 = 56760
Step 89: 56760 + 645 = 57405
Step 90: 57405 + 645 = 58050
Step 91: 58050 + 645 = 58695
Step 92: 58695 + 645 = 59340
Step 93: 59340 + 645 = 59985
Step 94: 59985 + 645 = 60630
Step 95: 60630 + 645 = 61275
Step 96: 61275 + 645 = 61920
Step 97: 61920 + 645 = 62565
Step 98: 62565 + 645 = 63210
Step 99: 63210 + 645 = 63855
Step 100: 63855 + 645 = 64500
Step 101: 64500 + 645 = 65145
Step 102: 65145 + 645 = 65790
Step 103: 65790 + 645 = 66435
Step 104: 66435 + 645 = 67080
Step 105: 67080 + 645 = 67725
Step 106: 67725 + 645 = 68370
Step 107: 68370 + 645 = 69015
Step 108: 69015 + 645 = 69660
Step 109: 69660 + 645 = 70305
Step 110: 70305 + 645 = 70950
Step 111: 70950 + 645 = 71595
Step 112: 71595 + 645 = 72240
Step 113: 72240 + 645 = 72885
Step 114: 72885 + 645 = 73530
Step 115: 73530 + 645 = 74175
Step 116: 74175 + 645 = 74820
Step 117: 74820 + 645 = 75465
Step 118: 75465 + 645 = 76110
Step 119: 76110 + 645 = 76755
Step 120: 76755 + 645 = 77400
Step 121: 77400 + 645 = 78045
Step 122: 78045 + 645 = 78690
Step 123: 78690 + 645 = 79335
Step 124: 79335 + 645 = 79980
Step 125: 79980 + 645 = 80625
Step 126: 80625 + 645 = 81270
Step 127: 81270 + 645 = 81915
Step 128: 81915 + 645 = 82560
Step 129: 82560 + 645 = 83205
Step 130: 83205 + 645 = 83850
Step 131: 83850 + 645 = 84495
Step 132: 84495 + 645 = 85140
Step 133: 85140 + 645 = 85785
Step 134: 85785 + 645 = 86430
Step 135: 86430 + 645 = 87075
Step 136: 87075 + 645 = 87720
Step 137: 87720 + 645 = 88365
Step 138: 88365 + 645 = 89010
Step 139: 89010 + 645 = 89655
Step 140: 89655 + 645 = 90300
Step 141: 90300 + 645 = 90945
Step 142: 90945 + 645 = 91590
Step 143: 91590 + 645 = 92235
Step 144: 92235 + 645 = 92880
Step 145: 92880 + 645 = 93525
Step 146: 93525 + 645 = 94170
Step 147: 94170 + 645 = 94815
Step 148: 94815 + 645 = 95460
Step 149: 95460 + 645 = 96105
Step 150: 96105 + 645 = 96750
Step 151: 96750 + 645 = 97395
Step 152: 97395 + 645 = 98040
Step 153: 98040 + 645 = 98685
Step 154: 98685 + 645 = 99330
Step 155: 99330 + 645 = 99975
Step 156: 99975 + 645 = 100620
Step 157: 100620 + 645 = 101265
Step 158: 101265 + 645 = 101910
Step 159: 101910 + 645 = 102555
Step 160: 102555 + 645 = 103200
Step 161: 103200 + 645 = 103845
Step 162: 103845 + 645 = 104490
Step 163: 104490 + 645 = 105135
Step 164: 105135 + 645 = 105780
Step 165: 105780 + 645 = 106425
Step 166: 106425 + 645 = 107070
Step 167: 107070 + 645 = 107715
Step 168: 107715 + 645 = 108360
Step 169: 108360 + 645 = 109005
Step 170: 109005 + 645 = 109650
Step 171: 109650 + 645 = 110295
Step 172: 110295 + 645 = 110940
Step 173: 110940 + 645 = 111585
Step 174: 111585 + 645 = 112230
Step 175: 112230 + 645 = 112875
Step 176: 112875 + 645 = 113520
Step 177: 113520 + 645 = 114165
Step 178: 114165 + 645 = 114810
Step 179: 114810 + 645 = 115455
Step 180: 115455 + 645 = 116100
Step 181: 116100 + 645 = 116745
Step 182: 116745 + 645 = 117390
Step 183: 117390 + 645 = 118035
Step 184: 118035 + 645 = 118680
Step 185: 118680 + 645 = 119325
Step 186: 119325 + 645 = 119970
Step 187: 119970 + 645 = 120615
Step 188: 120615 + 645 = 121260
Step 189: 121260 + 645 = 121905
Step 190: 121905 + 645 = 122550
Step 191: 122550 + 645 = 123195
Step 192: 123195 + 645 = 123840
Step 193: 123840 + 645 = 124485
Step 194: 124485 + 645 = 125130
Step 195: 125130 + 645 = 125775
Step 196: 125775 + 645 = 126420
Step 197: 126420 + 645 = 127065
Step 198: 127065 + 645 = 127710
Step 199: 127710 + 645 = 128355
Step 200: 128355 + 645 = 129000
Step 201: 129000 + 645 = 129645
Step 202: 129645 + 645 = 130290
Step 203: 130290 + 645 = 130935
Step 204: 130935 + 645 = 131580
Step 205: 131580 + 645 = 132225
Step 206: 132225 + 645 = 132870
Step 207: 132870 + 645 = 133515
Step 208: 133515 + 645 = 134160
Step 209: 134160 + 645 = 134805
Step 210: 134805 + 645 = 135450
Step 211: 135450 + 645 = 136095
Step 212: 136095 + 645 = 136740
Step 213: 136740 + 645 = 137385
Step 214: 137385 + 645 = 138030
Step 215: 138030 + 645 = 138675
Step 216: 138675 + 645 = 139320
Step 217: 139320 + 645 = 139965
Step 218: 139965 + 645 = 140610
Step 219: 140610 + 645 = 141255
Step 220: 141255 + 645 = 141900
Step 221: 141900 + 645 = 142545
Step 222: 142545 + 645 = 143190
Step 223: 143190 + 645 = 143835
Step 224: 143835 + 645 = 144480
Step 225: 144480 + 645 = 145125
Step 226: 145125 + 645 = 145770
Step 227: 145770 + 645 = 146415
Step 228: 146415 + 645 = 147060
Step 229: 147060 + 645 = 147705
Step 230: 147705 + 645 = 148350
Step 231: 148350 + 645 = 148995
Step 232: 148995 + 645 = 149640
Step 233: 149640 + 645 = 150285
Step 234: 150285 + 645 = 150930
Step 235: 150930 + 645 = 151575
Step 236: 151575 + 645 = 152220
Step 237: 152220 + 645 = 152865
Step 238: 152865 + 645 = 153510
Step 239: 153510 + 645 = 154155
Step 240: 154155 + 645 = 154800
Step 241: 154800 + 645 = 155445
Step 242: 155445 + 645 = 156090
Step 243: 156090 + 645 = 156735
Step 244: 156735 + 645 = 157380
Step 245: 157380 + 645 = 158025
Step 246: 158025 + 645 = 158670
Step 247: 158670 + 645 = 159315
Step 248: 159315 + 645 = 159960
Step 249: 159960 + 645 = 160605
Step 250: 160605 + 645 = 161250
Step 251: 161250 + 645 = 161895
Step 252: 161895 + 645 = 162540
Step 253: 162540 + 645 = 163185
Step 254: 163185 + 645 = 163830
Step 255: 163830 + 645 = 164475
Step 256: 164475 + 645 = 165120

So, 645*256 = 165120