Here is a spreadsheet to calculate the string needed for option 121 on a DHCP server.
DHCP option 121 is for distribution of IPv4 classless static routes to clients or why not between routers. Mikrotik DHCP client support it.
I did collect some important information about option 121 that are spread over Internet or that follow my experiments.
There are a couple online calculators available but they do not support /32 masks for the destination network.
Building the option 121 string is a bit tricky because of the hex conversion plus network address shortening (by 8 bits frontiers), so i did add a teaching version string to explain its structure.
Happy new year !