1.Luca held up a piece of paper. "The serial number of my new transistor," he said. "It's a funny number." "Funny?" Henrik asked. "How's that?" "Look," replied the boy. "When you shift the last three digits and put them in front of the other three, in the same order, you multiply it by six." That did make it rather special. What was the number?

Luca's number was 121897

Luca's number was 142857

Luca's number was 162352