Problem 26: Reciprocal Cycles (420ms)

Link: http://projecteuler.net/problem=26

Explanation: The number with longest recurring decimal will be prime.
Problem 28: Number Spiral Diagonals (6ms)

Link: http://projecteuler.net/problem=28
Problem 29: Distinct powers (28ms)

Link: http://projecteuler.net/problem=29
Problem 30: Digit Fifth power (9s)

Link: http://projecteuler.net/problem=30

Explanation : As 999999 > 9^5*6(354295), this means that all the numbers
whose sum of digit's 5th power are equal to the number itself will be
less than 999999.
Problem 32: Pandigital products (145ms)

Link: http://projecteuler.net/problem=32
Problem 34: Digit Factorials (4min)

Link: http://projecteuler.net/problem=34

Explanation : As 9999999 > 9!*7...So the max curious number possible
will be a 7 digit number.
Problem 35: Circular Primes (1s)

Link: http://projecteuler.net/problem=35

Explanation: The following points are taken into consideration for the
algo.
1) Use sieve to generate prime numbers till N
2) Start the algo for prime values>10
3) Do not loop over values already checked
4) Check if the prime number contains even digit before circular prime
check
5) Use sets inorder to check whether list of circular primes are
contained in prime list. This reduces a loop to check if all the values
in the list of rotations are in the list of primes.
Problem 36: Double-base Palindromes (329ms)

Link: http://projecteuler.net/problem=36

Explanation: Every even digit palindrome is divisible by 11.
Problem 37: Truncatable primes (550ms)

Link: http://projecteuler.net/problem=36
Problem 48: Self powers (17ms)

Link: http://projecteuler.net/problem=48
Problem 49: Prime permutations (50ms)

Link: http://projecteuler.net/problem=49
Problem 50: Consecutive prime sum (38s)

Link: http://projecteuler.net/problem=50