Basic Number Based Problems
1. Positive or Negative Numbers
2. Even or Odd Numbers
3. Sum of First N Natural numbers
4. Sum of N natural numbers
5. Sum of numbers in a given range
6. Greatest of two numbers
7. Greatest of the Three numbers
8. Leap year or not
9. Prime number
10. Prime number within a given range
11. Sum of digits of a number
12. Reverse of a number
13. Palindrome Number
14. Armstrong Number
15. Armstrong Number in a given range
16. Fibonacci Series upto nth term
17. Find the Nth Term of the Fibonacci Series
18. Factorial of a number
19. Power of a number
20. Factor of a number
21. Finding Prime Factors of a number
22. Strong number
23. Automorphic number
24. Harshad number
25. Abundant number
26. Friendly pair
Number-Based Problems
1. Spy Number: check if the sum of digits equals the product of digits for a given number. Print all Spy numbers up to N.
2.Magic Number: a number is Magic if recursively summing its digits yields 1. Check if N is a Magic number.
3.Happy Number: repeatedly replace N with the sum of squares of its digits. Detect if N eventually reaches 1.
4.Perfect Number: a number equals the sum of its proper divisors. Find all Perfect numbers up to N.
5.Perfect Square: check if a number is a perfect square without using sqrt().
6.Neon Number: the sum of digits of N-squared equals N itself (e.g. 9: 9²=81, 8+1=9). Find all Neon numbers in [1, 1000].
7.Buzz Number: a number divisible by 7 or ending in 7. Print all Buzz numbers in a given range [L, R].
8.Tribonacci Series: generate first N terms where T(n) = T(n-1)+T(n-2)+T(n-3). Also generate the Padovan and Jacobsthal series.
9 Krishnamurthi / Strong Number: sum of factorials of digits equals the number. Find all Strong numbers up to N.
10 Evil Number: numbers whose binary has an even number of 1-bits. In range [L,R] count how many are Evil vs Odious. Also identify Strobo-strategic numbers in the same range.
11 Pronic Number: product of two consecutive integers. Find all Pronic numbers in [1, N].
12 Unique Number: no digit repeats. Print all unique 3-digit numbers (100–999).
13 Nelson Number (111): check if N is 111 or a multiple pattern. Generalise: find all repunit numbers up to N.
14 Peterson Number: equals the sum of factorials of its digits raised to the power of their 1-based position. Check if N is a Peterson number.
15 Given a range [L, R], find all numbers that are simultaneously a Perfect Square AND a Perfect number.
