Pushups for keeping fit

I want to know if push-ups are enough for keeping fit. I can only do 15 push-ups at a time. Is this enough? I am a 60-year-old man.

Lekan (by SMS)

The main benefit of push-ups is that they build total body fitness using absolutely zero equipment. There are also plenty of pushup variations you can explore. You can even add weight by swinging on a rucksack or wearing a weighted vest. With pushups, you can do them anywhere.

Push-ups might seem simple, but they’re a highly effective exercise. It trains your whole body to work together as a unit, which makes you more functional than bench pressing or doing an incline dumbbell press.