123456789 is a `hidden beast` number, since 1 + 2 + 3 + 4 + 567 + 89 = 666.
123456789 is an esthetic number in base 10, because in such base it adjacent digits differ by 1.
It is an alternating number because its digits alternate between odd and even.
It is a straight-line number, since its digits are in arithmetic progression.
It is a plaindrome in base 10.
It is a congruent number.
It is an upside-down number.
Almost surely, 2123456789 is an apocalyptic number.
It is an amenable number.
123456789 is a wasteful number, since it uses less digits than its factorization.
123456789 is an evil number, because the sum of its binary digits is even.
The square root of 123456789 is about 11111.1110605556. Note that the first 3 decimals coincide. The cubic root of 123456789 is about 497.9338592182.
The spelling of 123456789 in words is "one hundred twenty-three million, four hundred fifty-six thousand, seven hundred eighty-nine".