Systems, apparatuses, and methods related to bit string accumulation are described. A method for bit string accumulation can include performing an iteration of a recursive operation using a first bit string and a second bit string and modifying a quantity of bits of a result of the iteration of the recursive operation, wherein the modified quantity of bits is less than a threshold quantity of bits. The method can further include writing a first value comprising the modified bits indicative of the result of the iteration of the recursive operation to a first register and writing a second value indicative of the factor corresponding to the result of the iteration of the recursive operation to a second register.