p-adic factors of base 10 prime

#include <iostream>
#include <cmath>

typedef unsigned long long uint64_t;


uint64_t find_b(uint64_t a, uint64_t target, uint64_t digits) {

    uint64_t guessDigit = 0;
    uint64_t guessLen = 0;
    uint64_t result = 0;


    for(int j=0;j<digits;j++){
        uint64_t p10=pow(10,1+guessLen); //base 10 shift by 10^n divison.
        uint64_t p10d=p10/10;

        for(uint64_t b=0;b<10;b++){ //test every base 10 digit
            uint64_t bg = b*p10d+result; //concatenate b-guess to lead of result, b=2 result=39 -> 2*100+39 -> 239
            uint64_t product = a * bg;
            if( (product%p10) == (target%p10) ){ //same trailing digits
                guessDigit=b;
                break;
            }
        }
        result+=guessDigit*(p10/10); //concat
        guessLen++;
    }

    return result;
}

int main() {
    for(uint a=1;a<32;a++){ //a is chosen
        uint64_t target = 13238717; // Target 10-adic number
        uint64_t leadingDigits = 6; //leading digits after minimum required precision
        uint64_t digits = log10(target)+1+leadingDigits; //target digit count
        uint64_t mod = pow(10, digits ); // ignore imprecise digits e.g. 3 * 33337746239 = 100013238717 -> ...00013238717

        uint64_t b = find_b(a, target, digits);

        std::string leadingZeros="";
        for(uint64_t i=0; i<leadingDigits;i++){
            leadingZeros+="0";
        }

        uint64_t approx = (a * b) % mod;
        if ( approx == target ) { //exclude impossible ones
            std::cout << a << " * ..." << b << " = ..." << leadingZeros << approx << std::endl;
        }
    }

    return 0;
}