When calculating the multiplication, Xiao Pang mistakenly regarded a factor of 51 as 15, and the result was 420. What is the correct number?
在计算乘法时，小胖错把一个因数51看成15，结果为420，原来正确得数是多少．
<gadget id="calculator">420 / 15</gadget>
<output>28</output>

<gadget id="calculator">28 * 51</gadget>
<output>1_428</output>

<result>1_428</result>