The number 642 is not a prime number as it can be divided by 2 aswell as itself and one.
They are: 2, 3 and 107
No, the first give-away is that it is an even number (divisible by 2).
Just by looking at it, without trying any factors to see if they work, you can see-- 642 is even, i.e. divisible by 2, since it ends in '2'-- 642 is divisible by 3, since its digits add up to (6+4+2) = 12 which is divisible by 3.Just looking at 642, you already know of at least 2 factors that it has besides '1' and itself,so it can't be a prime number.
642 is composite. It is divisible by 2, 3, 107, 214, and 321.
1, 2, 3, 6, 107, 214, 321, 642
1, 2, 3, 6, 107, 214, 321, 642 2, 3 and 107 are prime.
In today's notation 642 = DCXLII in Roman numerals
Nope, a 742 centerfire but no 642.
1 x 642, 2 x 321, 3 x 214, 6 x 107.
642 642
987 - 345 = 642