$2100 = 7 * 3 * 2^{2} * 5^{2}$
To calculate the total number of divisors, take each power in the prime factorization obtained, and:
Step 1: Increment the power.
$(1+1) (1+1) (2+1) (2+1)$
Step 2: Calculate the product of it:
$(1+1) * (1+1) * (2+1)* (2+1)$
Answer: 36