 It is significantly more difficult than primality testing, and although many factorization algorithms are known, they are slower than the fastest primality testing methods.Trial division and Pollard's rho algorithm can be used to find very small factors of formula_1, and elliptic curve factorization can be effective when formula_1 has factors of moderate size.Methods suitable for arbitrary large numbers that do not depend on the size of its factors include the quadratic sieve and general number field sieve.