2. Multiply each bit by its corresponding power of 2 and add all the terms up.
1101 1000 1100 1001 1111 0010 1010 1001 1111 0001 0000 0000 1111 1111 1111 0101(2) =
(1 × 263 + 1 × 262 + 0 × 261 + 1 × 260 + 1 × 259 + 0 × 258 + 0 × 257 + 0 × 256 + 1 × 255 + 1 × 254 + 0 × 253 + 0 × 252 + 1 × 251 + 0 × 250 + 0 × 249 + 1 × 248 + 1 × 247 + 1 × 246 + 1 × 245 + 1 × 244 + 0 × 243 + 0 × 242 + 1 × 241 + 0 × 240 + 1 × 239 + 0 × 238 + 1 × 237 + 0 × 236 + 1 × 235 + 0 × 234 + 0 × 233 + 1 × 232 + 1 × 231 + 1 × 230 + 1 × 229 + 1 × 228 + 0 × 227 + 0 × 226 + 0 × 225 + 1 × 224 + 0 × 223 + 0 × 222 + 0 × 221 + 0 × 220 + 0 × 219 + 0 × 218 + 0 × 217 + 0 × 216 + 1 × 215 + 1 × 214 + 1 × 213 + 1 × 212 + 1 × 211 + 1 × 210 + 1 × 29 + 1 × 28 + 1 × 27 + 1 × 26 + 1 × 25 + 1 × 24 + 0 × 23 + 1 × 22 + 0 × 21 + 1 × 20)(10) =
(9 223 372 036 854 775 808 + 4 611 686 018 427 387 904 + 0 + 1 152 921 504 606 846 976 + 576 460 752 303 423 488 + 0 + 0 + 0 + 36 028 797 018 963 968 + 18 014 398 509 481 984 + 0 + 0 + 2 251 799 813 685 248 + 0 + 0 + 281 474 976 710 656 + 140 737 488 355 328 + 70 368 744 177 664 + 35 184 372 088 832 + 17 592 186 044 416 + 0 + 0 + 2 199 023 255 552 + 0 + 549 755 813 888 + 0 + 137 438 953 472 + 0 + 34 359 738 368 + 0 + 0 + 4 294 967 296 + 2 147 483 648 + 1 073 741 824 + 536 870 912 + 268 435 456 + 0 + 0 + 0 + 16 777 216 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 32 768 + 16 384 + 8 192 + 4 096 + 2 048 + 1 024 + 512 + 256 + 128 + 64 + 32 + 16 + 0 + 4 + 0 + 1)(10) =
(9 223 372 036 854 775 808 + 4 611 686 018 427 387 904 + 1 152 921 504 606 846 976 + 576 460 752 303 423 488 + 36 028 797 018 963 968 + 18 014 398 509 481 984 + 2 251 799 813 685 248 + 281 474 976 710 656 + 140 737 488 355 328 + 70 368 744 177 664 + 35 184 372 088 832 + 17 592 186 044 416 + 2 199 023 255 552 + 549 755 813 888 + 137 438 953 472 + 34 359 738 368 + 4 294 967 296 + 2 147 483 648 + 1 073 741 824 + 536 870 912 + 268 435 456 + 16 777 216 + 32 768 + 16 384 + 8 192 + 4 096 + 2 048 + 1 024 + 512 + 256 + 128 + 64 + 32 + 16 + 4 + 1)(10) =
15 621 283 594 218 045 429(10)
The number 1101 1000 1100 1001 1111 0010 1010 1001 1111 0001 0000 0000 1111 1111 1111 0101(2) converted from an unsigned binary (in base 2) and written as a positive integer (with no sign) in decimal system (in base ten):
1101 1000 1100 1001 1111 0010 1010 1001 1111 0001 0000 0000 1111 1111 1111 0101(2) = 15 621 283 594 218 045 429(10)
Spaces were used to group digits: for binary, by 4, for decimal, by 3.