program isprime
	sca n = `0'
	sca p = 1
	if n<5 {
		if n!=2 & n!=3 {
			sca p = 0
		}
	}
	else {
		if mod(n, 2)==0 {
			sca p = 0
		}
		else {
			sca k=3
			while k*k<=n {
				if mod(n, k)==0 {
					sca p = 0
					continue, break
				}
				sca k = k+2
			}
		}
	}
	
	if p {
		di "`n' is prime."
	}
	else {
		di "`n' is not prime."
	}
end

isprime `=10^12-11'
999999999989 is prime.