Arithmetic gives you a clean, checkable digit. "Spiritual" is not a clean, checkable word — it means something different depending on who's using it, which makes this one of the harder rankings numerology attempts.
Even so, the tradition has a strong consensus pick: 7, consistently cast as the seeker, the introvert who turns inward before turning outward. Master numbers complicate the picture — 33 in particular is sometimes elevated above 7 for readers who favor a service-oriented definition of spirituality over an introspective one.
