Why 3 power to n will always get a sum of digit equal to 9?
126124
Why is the sum of the digits in a multiple of 9 also a multiple of 9?
116054
The number $(3+\sqrt{5})^n+(3-\sqrt{5})^n$ is an integer
112319
Sieve of Eratosthenes : why $\sqrt n$ work?
132728
Can the sum of the first $p$ factorials ever be a perfect power for $\ p>3\ $?
131708
Sum of powers of natural numbers
44799
Why is the even root of a number always positive?
142757
Math.pow with negative numbers and non-integer powers
140359
Can the sum of finitely many inverses of distinct odd integers $\geq 3$ be 1?
10744
Prove that a number is divisible by 3 iff the sum of its digits is divisible by 3
64592
The last two digits of $9^{9^9}$
42706
How many $N$ digits binary numbers can be formed where $0$ is not repeated
626
Sum of combinations with varying $n$
54442
Sum of $k {n \choose k}$ is $n2^{n-1}$
90032
Problem on Sum of Digits of a Number
17213
what operation repeated $n$ times results in the addition operator?
93572
How to determine if $n (n \geq 2)$ given numbers can be summed up to a certain number?
19
Why is the square root of a sum not equal to the square root of each its addends?