The direct arithmetic answer is about 5:41 per kilometre or 9:10 per mile, with an average speed of 10.55 km/h. The calculation uses the exact 21,097.5-metre distance, including the final 97.5 metres, so the displayed rounded pace is not substituted back into the total.
Divide 2:00:00 by the exact distance
2 hours = 7,200 seconds. 7,200 ÷ 21.0975 = about 341.2727 seconds per kilometre, which displays as 5:41/km. The exact distance is 21.0975 km = 21,097.5 m = 21,097,500,000 µm.
Read the rounded pace carefully
Exact pace is about 341.2727 seconds per kilometre, displayed as 5:41/km. Per mile it is about 549.938 seconds, displayed as 9:10/mi. Average speed is about 10.55 km/h or 6.56 mph. Multiplying displayed 5:41 by 21.0975 would not return exactly two hours.
Preserve the 21.0975 km finish
Useful cumulative checks include about 28:26 at 5 km, 56:53 at 10 km, 1:25:19 at 15 km, and 1:53:45 at 20 km. The final partial row at 21.0975 km is exactly 2:00:00 after display rounding. The table is an even arithmetic reference, not a pacing prescription.