Problem 19: Counting Sundays (1ms)

Link: http://projecteuler.net/problem=19
Problem 20: Factorial digit sum (6ms)

Link: http://projecteuler.net/problem=20
Problem 21: Amicable Numbers (1s)

Link: http://projecteuler.net/problem=21

Note: A simple brute force approach with minor optimization of the algo
by assigning the already checked amicable numbers to zero.
Problem 22: Names Scores (114ms)

Link: http://projecteuler.net/problem=22
Problem 23: Non-abundant sums (2.3s)

Link: http://projecteuler.net/problem=23
Problem 24: Lexicographic permutations (905ms)

Link: http://projecteuler.net/problem=24
Problem 25: 1000 digit Fibonacci number (112ms)

Link: http://projecteuler.net/problem=25