Northern Mariana Islands is about 870 times smaller than California.

California is approximately 403,882 sq km, while Northern Mariana Islands is approximately 464 sq km, making Northern Mariana Islands 0.11% the size of California. Meanwhile, the population of California is ~37.3 million people (37.2 million fewer people live in Northern Mariana Islands).
Tip: This to-scale comparison of California vs. Northern Mariana Islands uses the Mercator projection, which distorts the size of regions near the poles.