What is harder to catch the faster you run?

I have thought of a number that is made up by using all the ten digits just once. Here are a few clues for you to guess my number:

First digits is divisible by 1.
First two digits are divisible by 2.
First three digits are divisible by 3.
First four digits are divisible by 4.
First five digits are divisible by 5.
First six digits are divisible by 6.
First seven digits are divisible by 7.
First eight digits are divisible by 8.
First nine digits are divisible by 9.
The number is divisible by 10.

Can you find out the number ?

You can hear me, but you can't touch or see me.

What am I?

An inspection by the superintendent of St. Joseph School was scheduled on the next day. The class teacher Jenifer knew that he would be asking questions from her class and she would have to choose a pupil to answer. To offer a perfect impression over him, the teacher explained certain instructions to the students to maximise the chances of getting correct answer every time.

What did she say to the students?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

What does this below rebus puzzle mean?

A father's child, a mother's child, yet no one's son.

Who am I?

Can you count the number of triangles in the given picture?