It leaves a remainder of 1 when divided by 2. Or, if the number is n, then n-1 or n+1 is even (divisible by 2).
There are no irrational integers - all integers can be represented as fractions with a denominator of 1.
The are an infinite number of rational numbers that are not integers, because a rational number is a number that is written as a ratio of two integers. For examble, 1/2 (i.e. a half) is a non-integer...
Integers are whole numbers. Rational numbers can be fractions / decimals. But it is NEVER a whole number E.G. of rational numbers : 3/4 or 1.5
Absolutely. As long as it can be expressed as a fraction with the denominator not being zero, and both numerator and denominator being integers.