Numbers / 61

The Number 61

61 is prime: only 1 and 61 divide it evenly; the next prime after 61 is 67. 61's proper divisors total just 1, 60 short of 61, the deficient case most of 61's neighbors share too. 61 has a digit sum of 7; for 61, the digital root works out to 7. 61 shares no factor with 2-12; 61's own divisors start beyond that range. 61 is 111101 in binary and 3D in hex; as a Roman numeral it's LXI.