The CAS Registry Mumber 70656-65-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,0,6,5 and 6 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 70656-65: (7*7)+(6*0)+(5*6)+(4*5)+(3*6)+(2*6)+(1*5)=134 134 % 10 = 4 So 70656-65-4 is a valid CAS Registry Number.