Check Composite Number in Python

Check whether a number is composite (non-prime, greater than 1).

BeginnerLoop ProgramsExample 14 of 25
check-composite-number.py
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1# Program to check if a number is composite
2
3n = int(input("Enter an integer: "))
4
5if n <= 1:
6 print(n, "is neither prime nor composite")
7else:
8 is_composite = False
9 for i in range(2, int(n ** 0.5) + 1):
10 if n % i == 0:
11 is_composite = True
12 break
13 if is_composite:
14 print(n, "is a composite number")
15 else:
16 print(n, "is not a composite number (it is prime)")

Output

Enter an integer: 9
9 is a composite number

What's going on

We look for any divisor between 2 and √n; if found, the number is composite.