A number system in which numbers are written as sums of successive powers of -3. The three digits are 0, 1, and 2. The advantage of using a negative radix is that there is no longer a need for a minus sign; negative numbers can be written the same way as positive numbers. (Compare balanced ternary in which the radix is positive 3 but the digits are -1, 0, and 1.) Here are the integers from negative ten to ten in both decimal and negaternary:

-10  1212
 -9  1200
 -8  1201
 -7  1202
 -6    20
 -5    21
 -4    22
 -3    10
 -2    11
 -1    12
  0     0
  1     1
  2     2
  3   120
  4   121
  5   122
  6   110
  7   111
  8   112
  9   100
 10   101
As in negabinary, negative numbers have an even number of digits, and positive numbers have an odd number of digits.