# online calculator for the Carmichael function

keywords:
[mathematics]
[relatively prime]
[coprime]
[relatively-prime]
[co-prime]
[prime factorization]
[function-value lookups]
[function-evaluation]
[function evaluation]

# online calculator for the totient function

(aka Euler’s phi function)
for example, φ(10) = 4, because 1, 3, 7, and 9 are relatively prime to 10
keywords:
[mathematics]
[relatively prime]
[coprime]
[relatively-prime]
[co-prime]
[prime factorization]
[multiplicative function]
[function-value lookups]
[function-evaluation]
[function evaluation]

# anagrammatic totient values

(or, ‘anagrammatic totients’ for short)
(suggested new terminology)
Definition. For numbers of a specified number of digits (padding with leading zeros if necessary), an anagrammatic totient value (or, an anagrammatic totient, for short) is a totient that is an anagram of the argument.
For example, for 4-digit numbers, Kaprekar’s constant, namely, 6174, has an anagrammatic totient, namely, 1764 (which, incidentally, is the year of Goldbach’s death).
keywords:
[Recreational Mathematics]
[Language Arts]
[the two worlds of C.P. Snow]
[Number Theory]
[Euler’s totient function]
[Euler’s φ function]
[totatives]
[relatively prime]
[coprime]
[relatively-prime]
[co-prime]

# the Kaprekar process

example:
then:
4210 – 0124 = 4086
8640 – 0468 = 8172
8721 – 1278 = 7443
7443 – 3447 = 3996
9963 – 3699 = 6264
6642 – 2466 = 4176
7641 – 1467 = 6174
Here is the Wikipedia article on this topic.
keywords:
[the Kaprekar routine]
[Kaprekar’s process]
[Kaprekar’s routine]
[Recreational Mathematics]
[Kaprekar’s constant]