diff --git a/R/16. Power digit sum/kkulma.R b/R/16. Power digit sum/kkulma.R
new file mode 100644
index 0000000..1e16f4f
--- /dev/null
+++ b/R/16. Power digit sum/kkulma.R	
@@ -0,0 +1,15 @@
+power_digit_sum <- function(num, ...) {
+  tidy_num <- formatC(num, ...)
+  num_char <- as.character(tidy_num)
+  num_split <- unlist(strsplit(num_char, split = ""))
+  sum(as.numeric(num_split))
+}
+
+# show that the example works
+power_digit_sum(2^15)
+
+# solution
+# 1200
+power_digit_sum(2^1000, format = "f", digits = 0)
+
+
diff --git a/R/19.Counting Sundays/kkulma.R b/R/19.Counting Sundays/kkulma.R
new file mode 100644
index 0000000..a09a0b3
--- /dev/null
+++ b/R/19.Counting Sundays/kkulma.R	
@@ -0,0 +1,12 @@
+library(lubridate)
+library(dplyr)
+
+base <- data.frame(
+  date = seq(as.Date("1901-01-01"), as.Date("2000-12-31"), by = "day")
+)
+
+# solution
+# 171
+base %>% 
+  dplyr::mutate(dname = lubridate::wday(date, label = TRUE)) %>% 
+  dplyr::filter(lubridate::day(date) == 1 & dname == "Sun")
diff --git a/R/20. Factorial digit sum/kkulma.R b/R/20. Factorial digit sum/kkulma.R
new file mode 100644
index 0000000..6ef4750
--- /dev/null
+++ b/R/20. Factorial digit sum/kkulma.R	
@@ -0,0 +1,15 @@
+power_digit_sum <- function(num, ...) {
+  tidy_num <- formatC(num, ...)
+  num_char <- as.character(tidy_num)
+  num_split <- unlist(strsplit(num_char, split = ""))
+  sum(as.numeric(num_split))
+}
+
+# show that the example works
+power_digit_sum(factorial(10), format = "f", digits = 0)
+
+# solution
+# 645
+power_digit_sum(factorial(100), format = "f", digits = 0)
+
+
diff --git a/R/24.Lexicographic permutations/kkulma.R b/R/24.Lexicographic permutations/kkulma.R
new file mode 100644
index 0000000..0e963e9
--- /dev/null
+++ b/R/24.Lexicographic permutations/kkulma.R	
@@ -0,0 +1,13 @@
+library(gtools)
+
+base <- 0:9
+
+# run permutations
+perm <- permutations(n = 10,
+             r = 10,
+             v = base)
+
+# solution
+# 2 7 8 3 9 1 5 4 6 0
+perm[1000000, ]
+
diff --git a/README.md b/README.md
index b794d72..b36a28c 100644
--- a/README.md
+++ b/README.md
@@ -45,15 +45,15 @@ Happy Contributing! 😃
 | 13 | [Large sum](https://projecteuler.net/problem=13)                             | :white_check_mark: |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
 | 14 | [Longest Collatz sequence](https://projecteuler.net/problem=14)              |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
 | 15 | [Lattice paths](https://projecteuler.net/problem=15)                         |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
-| 16 | [Power digit sum](https://projecteuler.net/problem=16)                       |                    | :white_check_mark: |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
+| 16 | [Power digit sum](https://projecteuler.net/problem=16)                       |                    | :white_check_mark: |                    | :white_check_mark: |                    |                    |                    |                    |                    | :white_check_mark: |                    |                    |
 | 17 | [Number letter counts](https://projecteuler.net/problem=17)                  |                    |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
 | 18 | [Maximum path sum I](https://projecteuler.net/problem=18)                    |                    |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
-| 19 | [Counting Sundays](https://projecteuler.net/problem=19)                      |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
-| 20 | [Factorial digit sum](https://projecteuler.net/problem=20)                   |                    | :white_check_mark: |                    | :white_check_mark: | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |
+| 19 | [Counting Sundays](https://projecteuler.net/problem=19)                      |                    |                    |                    |                    |                    |                    |                    |                    |                    | :white_check_mark: |                    |                    |
+| 20 | [Factorial digit sum](https://projecteuler.net/problem=20)                   |                    | :white_check_mark: |                    | :white_check_mark: | :white_check_mark: |                    |                    |                    |                    | :white_check_mark: |                    |                    |
 | 21 | [Amicable numbers](https://projecteuler.net/problem=21)                      |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
 | 22 | [Names scores](https://projecteuler.net/problem=22)                          |                    |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
 | 23 | [Non-abundant sums](https://projecteuler.net/problem=23)                     |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
-| 24 | [Lexicographic permutations](https://projecteuler.net/problem=24)            |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
+| 24 | [Lexicographic permutations](https://projecteuler.net/problem=24)            |                    |                    |                    |                    |                    |                    |                    |                    |                    | :white_check_mark: |                    |                    |
 | 25 | [1000-digit Fibonacci number](https://projecteuler.net/problem=25)           |                    |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
 | 26 | [Reciprocal cycles](https://projecteuler.net/problem=26)                     |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
 | 27 | [Quadratic primes](https://projecteuler.net/problem=27)                      |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |