A prime number is a whole number, greater than 1, that only has two factors. A factor is a number that divides another number evenly, with no remainder or decimal. The factors of a prime number are ...

May 30 (UPI) --A shard of smooth bone etched with irregular marks dating back 20,000 years puzzled archaeologists until they noticed something unique - the etchings, lines like tally marks, may have ...