Fifty-one is three times seventeen and reduces to six. Its firmest association is Psalm 51, the Miserere, the great psalm of repentance ascribed to David after the prophet Nathan confronted him over Bathsheba, Have mercy upon me, O God, according to thy lovingkindness, which became a central penitential text in both Jewish and Christian liturgy and was set to music most famously by Gregorio Allegri for the Sistine Chapel. Beyond the psalm, fifty-one carries no developed traditional symbolism; it is a composite number that the older systems passed over.
Cheiro's 1926 Book of Numbers gives fifty-one a description of its own rather than pointing back to a lower number: strong fortune, or at least a greater ease in overcoming conflict and challenge, one of the more favourable readings among the higher compound numbers in his scheme and, since Cheiro's original compound-number scheme runs only from ten to fifty-two, one of the last individually described figures before the pattern of pointing back to earlier numbers, already seen throughout this family of articles, takes over almost entirely. In chemistry, fifty-one is the atomic number of antimony, whose symbol, Sb, comes from its old Latin name stibium; antimony compounds served as the black cosmetic eyeliner kohl in the ancient Near East and Egypt long before the element was isolated and formally named.