It is not possible to answer the question without information about the number of significant figures required.
12,437 rounded to four significant figures = 12,440
5 of them.
It is 6.7 when rounded to 2 significant figures
You didn't say how many significant figures. But, rounded to six significant figures it would be 5206.00
At least 1 and at most 7. It could be 3,999,999.9 rounded to 7 significant figures; It could be 3,999,999 rounded to 6 significant figures; It could be 4,000,015 rounded to 5 significant figures; It could be 4,000,429 rounded to 4 significant figures; It could be 3,999,999 rounded to 3 significant figures; It could be 4,049,999 rounded to 2 significant figures; It could be 4,492,467 rounded to 1 significant figure.
0.00721004 rounded into three significant figures is 0.00721
16.275 rounded to 3 significant figures is 16.3
79,966.92 rounded to three significant figures is 8.00e4
0.00721004 rounded to three significant figures is 0.00721
44.981 rounded to three significant figures is 45.0
0.000709999 rounded to 3 significant figures is 0.000710
223.4016 rounded five significant figures is 223.40