How many digits are there in $99^{99}$?
51299
How many digits is $99^{99}$ without a calculator?
90952
Does every number not ending with zero have a multiple without zero digits at all?
3128
Why $9$ & $11$ are special in divisibility tests using decimal digit sums? (casting out nines & elevens)
11447
How many $4$ digit even numbers have all $4$ digits distinct?
37873
Number of zero digits in factorials
853
Write down the sum of sum of  sum of digits of $4444^{4444}$
13857
Why (directly!) does every number divide 9, 99, 999, ... or 10, 100, 1000, ..., or their product?
150652
Number of 4-digit numerals with at most 2 different digits
71047
Sum the digits of a number
113950
Formula for reversing digits of positive integer $n$
121614
Count how many number are there from $1$ to $N$ who have all $10$ digits in it at least once.
132928
Digits of $\pi$ forming primes?
26701
Is there a reliable way in JavaScript to obtain the number of decimal places of an arbitrary number?
142135
A number with 6 distinct digits which get multiplied by 5 if we move the last digit to front
40821
Number formation from given digits
49116
Finding the last digit of $103^{103^{103^{103^{103}}}}$
25181
Simple numerical methods for calculating the digits of $\pi$