Meaning
2121 alternates the cooperative 2 with the initiating 1. It's read as starting something new together rather than alone.
In love & friendship
Begin a new ritual with someone you love.
In work & purpose
Pitch the idea to a partner instead of going solo.
In numerology
The digits of 2121 add up to 6, which reduces to 6: the nurturer: care, home, responsibility.
Sit with this: Who could you start something with?