Is 1637143983 prime or composite

Answer 1

1637143983 is not prime. Its prime factorisation is: 3 × 3 × 7321 × 24847.

In the case of this number and one ninth of all integers, the fact that it is composite can be quickly determined by calculating the core digit value, the sum of all digits reduced to one digit. The core digit value of this number is 9, and every single integer with this core digit value is a multiple of 9. This can only prove that a number is composite. A core digit value other than 9 does not prove that a number is prime.