pqr = 100p + 10q + r
qrp = 100 q + 10r + p
rpq = 100r + 10p + q
Adding all three,
⇒ pqr + qrp + rpq = 100(p + q +r) + 10(p + q + r) + (p + q + r) = 111 (p + q +r) = 37 × 3 (p + q + r)
(pqr + qrp + rpq) is always divisible by 1, 3, 37, 111 and (p + q + r).