Let N is the least number of 6 digits, which when divide by 4, 5, 6, 10 and 15 leaves the remainder 3 in each case.  Find the sum of digits in N.

6

LCM of 4, 5, 6, 10, 15 = 60

The least number of 6 digits = 100000

After dividing 100000 by 60, the remainder = 40

∴ The least six digits number divisible by 60 = 100000 + 20 = 100020

(N) required number = 100020 + 3 = 100023

Sum of digits of N = 1 + 2 + 3 = 6