A bit of factoring history...
1971 The big news was the factoring of a 41 digit number.
1991 RSA Data Security Inc set up RSA Factoring Challenge: list of hard numbers, each product of 2 primes, ranging from 100 digits to 500 digits.
1994 “RSA129”, one of challenge numbers, 129 digits (428) bits), factored over 8 months, using 1600 computers on Internet around the world (~5000 MIPS-years)
“We conclude that commonly used 512-bit RSA moduli are vulnerable to any organization prepared to spend a few million dollars and to wait a few months.”
With this method, a 250-digit number would take 100,000,000 times as long.