• 648 is the smallest number that cannot be obtained by concatenating the absolute differences of adjacents digits of a larger number. For example, 647 can be obtained from 9370, because |9-3| = 6, |3-7| = 4, and |7-0| = 7.
Adding to 648 its sum of digits (18), we get a palindrome (666).
Subtracting from 648 its sum of digits (18), we obtain a triangular number (630 = T35).
Multipling 648 by its sum of digits (18), we get a square (11664 = 1082).
648 divided by its sum of digits (18) gives a triangular number (36 = T8).
648 is an esthetic number in base 8, because in such base its adjacent digits differ by 1.
It is an ABA number since it can be written as A⋅BA, here for A=3, B=6.
It is a nude number because it is divisible by every one of its digits.
It is a plaindrome in base 13, base 14 and base 16.
It is a nialpdrome in base 3, base 6 and base 9.
It is a zygodrome in base 3.
It is a self number, because there is not a number n which added to its sum of digits gives 648.
2648 is an apocalyptic number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 648
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
648 is a wasteful number, since it uses less digits than its factorization.
648 is an odious number, because the sum of its binary digits is odd.
The square root of 648 is about 25.4558441227. The cubic root of 648 is about 8.6534974218.
The spelling of 648 in words is "six hundred forty-eight", and thus it is an aban number.