By splitting into prime factors, find the square root of 396900.

$396900 = (2 \times 2) \times (3 \times 3) \times (3 \times 3) \times (5 \times 5) \times (7 \times 7)\\[1em] ⇒ \sqrt{396900} = 2 \times 3 \times 3 \times 5 \times 7\\[1em] ⇒ \sqrt{396900} = 630$

Square root of 396900 is 630.