The CAS Registry Mumber 125974-42-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,5,9,7 and 4 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 125974-42: (8*1)+(7*2)+(6*5)+(5*9)+(4*7)+(3*4)+(2*4)+(1*2)=147 147 % 10 = 7 So 125974-42-7 is a valid CAS Registry Number.