Find the smallest regular number that is not less than N

Question

Regular numbers are numbers that evenly divide powers of 60. As an example, 60² = 3600 = 48 × 75, so both 48 and 75 are divisors of a power of 60.

Answer 1

I wrote a small c# program to solve this problem. It's not very optimised but it's a start. This solution is pretty fast for numbers as big as 11 digits.

private long GetRegularNumber(long n)
{
    long result = n - 1;
    long quotient = result;

    while (quotient > 1)
    {
        result++;
        quotient = result;

        quotient = RemoveFactor(quotient, 2);
        quotient = RemoveFactor(quotient, 3);
        quotient = RemoveFactor(quotient, 5);
    }

    return result;
}

private static long RemoveFactor(long dividend, long divisor)
{
    long remainder = 0;
    long quotient = dividend;
    while (remainder == 0)
    {
        dividend = quotient;
        quotient = Math.DivRem(dividend, divisor, out remainder);
    }
    return dividend;
}