ᶲ(35)= A. 24 B. 25 C. 22 D. 18 This question was addressed to

35-a-24-b-25-c-22-d-18-this-question-was-addressed-to

ᶲ(35)=

A. 24

B. 25

C. 22

D. 18

This question was addressed to me in final exam.

My question is taken from Number Theory topic in division More Number Theory of Cryptograph & Network Security

Right answer is A. 24

The best explanation: ᶲ(36) = 24 = 6 x 4. These are the numbers which are relatively prime  –

1,2,3,4,6,8,9,11,12,13,16,17,18,19,22,23,24,26,27,29,31,33,34.