Primes in an Infinite Sequence
1.) Given the following infinite sequence:
9, 98, 987, 9876, ..., 987654321, 9876543219, 98765432198, ...
What are all the primes?
2.) David has this unique social security number. The 9 digits in the social security number have the digits from 1 all the way through 9. The number also has the following properties: when you read it from left to right, the first two digits will form a number that is divisible by 2, the first 3 digits will form a number that's divisible by 3, the first 4 digits... and so forth until the whole number is divisible by 9. What is David's social security number?