10 is the integer the proceeds 9 and preceeds 11 It's prime factorization is 2*5. A number is divisible by 10 if the last digit ends with a 0. 10 is also the smallest 2 digit number. 10 is the smallest number whose status is unknown whether it is solitary or friendly. The numbers 1 through 5 are all solitary. 6 is the first friendly number. The numbers 7 through 9 are all solitary.