3×5×7+7 = 7(3×5+1) = 7×16 = 7×2×2×2×2×1.Clearly, It has more than two factors.So, it is a composite number

Introduction:
In mathematics, a composite number is a positive integer that has at least one divisor other than 1 and itself. It is a number that can be divided evenly by numbers other than 1 and itself. In this case, we are given 3 × 5 × 7, and we need to determine whether it is a composite number or not.

Prime Factorization:
To determine if 3 × 5 × 7 is a composite number, we first need to find its prime factorization. Prime factorization is the process of finding the prime numbers that multiply together to give a certain number. In this case, we need to find the prime factors of 3, 5, and 7.

Prime Factors:
- The prime factorization of 3 is 3 itself because 3 is a prime number.
- The prime factorization of 5 is 5 itself because 5 is a prime number.
- The prime factorization of 7 is 7 itself because 7 is a prime number.

Composite Number:
A composite number is a number that has more than two factors. In this case, we have the factors 3, 5, 7, 3 × 5, 3 × 7, and 5 × 7. Therefore, 3 × 5 × 7 has more than two factors, making it a composite number.

Conclusion:
In conclusion, 3 × 5 × 7 is a composite number because it has more than two factors. It can be divided evenly by numbers other than 1 and itself, which are 3, 5, 7, 3 × 5, 3 × 7, and 5 × 7.