This number is better-known as RSA-129.
It was posted in a 1977 magazine article as a challenge.
The co-inventors of RSA Cryptography wanted to see just how hard it was to factorize a number (it was crucial to the new technology).
RSA-129 is created by multiplying two very large prime numbers.
Ron Rivest (the R in RSA) thought it would take 40 quadrillion years for the prime numbers to be found.
He was wrong. It took 17 years.