13th root 13th root of a 100-digit number. All world records for mentally extracting a 13th root have been for numbers with an integer root. 13th root Extracting the 13th root of a number is a famous category for the mental calculation world records. The challenge consists of being given a large number (possibly over 100 digits) and asked to return the number that, when taken to the 13th power, equals the given number. For example, the 13th root of 8,192 is 2 and the 13th root of 96,889,010,407 is 7. Extracting the 13th root has certain properties. One is that the
British Rail Class 401 Full details of the 7-TC formation, the origin of the individual cars and their subsequent disposal are set out in the table below: Only one 2-BIL unit has survived into preservation, namely number 2090, formed of carriages 10656 and 12123, which is in the care of the National Railway Museum, York. This unit is also one of only two pre-war main line EMUs in existence, which are still in original formation. The other is the Class 503, which is kept at the Electric Railway Museum near Coventry. British Rail Class 401 The Southern Railway (SR) gave the designation 2-BIL to