Complex sentence: RSA-640 has a length of 193 decimal digits and has not been factored so far; a cash prize of $20,000 USD has been offered successful factorisation by RSA Security.
Split into simpler sentences: RSA-640 has a length of 193 decimal digits and has not been factored so far. A cash prize of 20,000 USD has been offered for successful factorisation by RSA Security.