There are some four-digit numbers that are 2 different odd numbers and 2 different even numbers, and do not contain the number 0. How many such four-digit numbers are there?
有一些四位数的4个数字分别是2个不同的奇数和2个不同的偶数，而且不含有数字0．这样的四位数有几个？
<gadget id="calculator">10 * 6 * 24</gadget>
<output>1_440</output>

<result>1_440</result>