If we assume that numbers go on forever, we have an example of infinity. But, odd numbers go on forever, though there are half as many odd numbers as there are numbers.
Numbers divisible by three also go on forever, but there only a third as many numbers that are divisible by three. Similarly, numbers divisible by five go on forever, but there are even fewer of them.
Catholic Fundamentalists see infinity in terms of “density”. Even the largest prime number known will have an infinite number of numbers into which it may be divided, but it will be a very “undense” infinity.
One way to determine “density” is to divide a number into a million, or a billion, or a trillion, or a quadrillion. The number of times it occurs gives an indication of its density. The larger the number into which it is divided, the more accurate an approximation of “density” we have to apply to infinity.