Round the number 621,144,010 down to the nearest tens, hundreds, thousands, and ten-thousands. Also, round 0.000598473212 to 3 significant figures.

Step 1: Round 621,144,010 down to the nearest tens.
Rounding down to the nearest tens means finding the largest multiple of 10 that is less than or equal to the number.
The number is already a multiple of 10.

$$621,144,010$$

Step 2: Round 621,144,010 down to the nearest hundreds.
Rounding down to the nearest hundreds means finding the largest multiple of 100 that is less than or equal to the number.
The hundreds digit is 0. The number is between 621,144,000 and 621,144,100.

$$621,144,000$$

Step 3: Round 621,144,010 down to the nearest thousands.
Rounding down to the nearest thousands means finding the largest multiple of 1000 that is less than or equal to the number.
The thousands digit is 4. The number is between 621,144,000 and 621,145,000.

$$621,144,000$$

Step 4: Round 621,144,010 down to the nearest ten-thousands.
Rounding down to the nearest ten-thousands means finding the largest multiple of 10,000 that is less than or equal to the number.
The ten-thousands digit is 4. The number is between 621,140,000 and 621,150,000.

$$621,140,000$$