A slightly odd layman's question about factoring large numbers and comparing two calculations.

Call N a number with 10^{50}digits.

1) Factorise N

2) Multiply the primes sequentially from 2 onwards until the product is as close as possible to N.

Would calculation 2 be significantly easier computationally than calculation 1?

How many digits would a number has to have before factorisation becomes a problem for our current methods?

Thanks