Euler's totient function
Definition from Wiktionary, the free dictionary
English[edit]
Etymology[edit]
Named after the 18^{th} century Swiss mathematician Leonhard Euler (17071783).
Noun[edit]
Euler's totient function (uncountable)
 (number theory) The function that counts how many integers below a given integer are coprime to it.
 Due to Euler's theorem, if f is a positive integer which is coprime to 10, then
where is Euler's totient function. Thus , which fact which may be used to prove that any rational number whose expression in decimal is not finite can be expressed as a repeating decimal. (To do this, start by splitting the denominator into two factors: one which factors out exclusively into twos and fives, and another one which is coprime to 10. Secondly, multiply both numerator and denominator by such a natural number as will turn the first said factor into a power of 10 (call it N). Thirdly, multiply both numerator and denominator by such a number as will turn the second said factor into a power of 10 minus one (call it M). Fourthly, resolve the numerator into a sum of the form . Then the repeating decimal has the form where b may be padded by zeroes (if necessary) to take up digits, and c may be padded by zeroes (if necessary) to take up digits.)
 Due to Euler's theorem, if f is a positive integer which is coprime to 10, then
Usage notes[edit]
 Usually denoted with the Greek letter phi ( or ).
Related terms[edit]
Translations[edit]
number theory

