The CAS Registry Mumber 105202-58-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,5,2,0 and 2 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 105202-58: (8*1)+(7*0)+(6*5)+(5*2)+(4*0)+(3*2)+(2*5)+(1*8)=72 72 % 10 = 2 So 105202-58-2 is a valid CAS Registry Number.