what are a, b, and c?

Note: Adjacent numerals are multi-digit numbers made of those numerals, not the product; i.e., if m=2 and n=3, then mn=23.

aaaaaa = a*(111111)

= a*3*37*11*7*13

fits nicely into b * c * bc * (c+c-b) * (c+b+b) * (c-b)

only thing missing is c-b which is a. Therefore a = 4.