# Numbers and their divisibility

version from 2015-12-17 03:10

## Section

prime noare not evenly divisible numbers, are divisible by one or itself
composite noare evenly divisible numbers, are multiples of prime numbers
coprime / relatively prime notwo numbers which have highest common factor 1
twin prime numberstwo prime numbers whose difference is 2
divisibility of 2last digit is even
divisibility of 3sum is divisible by 3
divisibility of 4last two digits are divisible by 4
divisibility of 5last digit is 0 or 5
divisibility of 6number is divisible by both 3 and 2
divisibility of 7double and subtract the last digit from rest number, the number obtained is either 0 or divisible by 7
divisibility of 8the last three digits are divisible by 8
divisibility of 9sum is divisible by 9
divisibility of 10last digit is 0
divisibility of 11add and subtract digits alternatively, the number obtained is either zero or multiple of 11
divisibility of 12should be divisible by both 3 and 4
log of zerodoes not exist
log of -ve not defined
who is excluded from the base of logarithm unity