The Chaldean Vibration Number comes from an older numerology system than the Pythagorean one used elsewhere on this site, developed in ancient Babylon and based on the sound value of each letter rather than its position in the alphabet. Unlike Pythagorean numbers, Chaldean numerology deliberately keeps the compound (two-digit) number rather than always reducing it to a single digit, since the compound number itself is considered to carry its own distinct meaning before any further reduction.

Chaldean 40 is traditionally considered a caution number, associated with obstacles and setbacks that test resolve, historically viewed as a difficult vibration.