10548158321

This number is a prime.

                                                                1 0548158321

The smallest prime formed by reverse concatenation of first n double factorials:

1!! = 1
2!! = 2
3!! = 3 x 1 = 3
4!! = 4 x 2 = 8
5!! = 5 x 3 x 1 = 15
6!! = 6 x 4 x 2 = 48
7!! = 7 x 5 x 3 x 1 = 105. [Gudipati]