Let's roll up our sleeves and solve this. We have 26 and we're going to multiply it by 21, essentially adding 26 to itself 21 times.
Step 1: 0 + 26 = 26
Step 2: 26 + 26 = 52
Step 3: 52 + 26 = 78
Step 4: 78 + 26 = 104
Step 5: 104 + 26 = 130
Step 6: 130 + 26 = 156
Step 7: 156 + 26 = 182
Step 8: 182 + 26 = 208
Step 9: 208 + 26 = 234
Step 10: 234 + 26 = 260
Step 11: 260 + 26 = 286
Step 12: 286 + 26 = 312
Step 13: 312 + 26 = 338
Step 14: 338 + 26 = 364
Step 15: 364 + 26 = 390
Step 16: 390 + 26 = 416
Step 17: 416 + 26 = 442
Step 18: 442 + 26 = 468
Step 19: 468 + 26 = 494
Step 20: 494 + 26 = 520
Step 21: 520 + 26 = 546

So, 26*21 = 546