The CAS Registry Mumber 1337880-15-5 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,3,3,7,8,8 and 0 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 1337880-15: (9*1)+(8*3)+(7*3)+(6*7)+(5*8)+(4*8)+(3*0)+(2*1)+(1*5)=175 175 % 10 = 5 So 1337880-15-5 is a valid CAS Registry Number.