Find the next number in the series below

21 32 54 87 131 ?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

My cousin lives in one story house in Antarctica. His house is made the of-of sandstone. what is the color of stairs?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

Once upon a time, there was a castle on a square island. The entire island was surrounded by a 14m wide trench. The Romans had wanted to invade the castle and had brought a few wooden planks along with them to facilitate themselves in crossing the moat. The planks were however found to be only 13m long.

The Romans still managed to cross the trench. How did they do it?

It is deaf, Dumb and Blind!!!

Still, always tells the truth. What is it?

Two friends were stuck in a cottage. They had nothing to do and thus they started playing cards. Suddenly the power went off and Friend 1 inverted the position of 15 cards in the normal deck of 52 cards and shuffled it. Now he asked Friend 2 to divide the cards into two piles (need not be equal) with equal number of cards facing up. The room was quite dark and Friend 2 could not see the cards. He thinks for a while and then divides the cards in two piles.

On checking, the count of cards facing up is same in both the piles. How could Friend 2 have done it ?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

Only one color, but not one size,
Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?