Numbers / 77

The Number 77

77 is composite: factorization 7 × 11. That gives 77 exactly 4 divisors: 1, 7, 11, 77. 77's proper divisors total just 19, 58 short of 77, the deficient case most of 77's neighbors share too. 77 is also a palindrome, since 77 reads identically forwards and backwards. 77 has a digit sum of 14; for 77, the digital root works out to 5. 77: 7, 11 all divide 77 evenly, out of 2-12. 77 is 1001101 in binary and 4D in hex; as a Roman numeral it's LXXVII.