The CAS Registry Mumber 1009715-74-5 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,0,0,9,7,1 and 5 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 1009715-74: (9*1)+(8*0)+(7*0)+(6*9)+(5*7)+(4*1)+(3*5)+(2*7)+(1*4)=135 135 % 10 = 5 So 1009715-74-5 is a valid CAS Registry Number.