1638 divided by its sum of digits (18) gives a triangular number (91 = T13).
Adding to 1638 its reverse (8361), we get a palindrome (9999).
1638 is nontrivially palindromic in base 16.
1638 is an esthetic number in base 4, because in such base its adjacent digits differ by 1.
It is a harmonic number, since the harmonic mean of its divisors is an integer.
1638 is an admirable number.
It is an alternating number because its digits alternate between odd and even.
1638 is an undulating number in base 4.
It is a Curzon number.
1638 is a nontrivial repdigit in base 16.
It is a plaindrome in base 11 and base 16.
It is a nialpdrome in base 9, base 13, base 14, base 15 and base 16.
It is a zygodrome in base 16.
It is a self number, because there is not a number n which added to its sum of digits gives 1638.
It is a congruent number.
21638 is an apocalyptic number.
1638 is a gapful number since it is divisible by the number (18) formed by its first and last digit.
It is a practical number, because each smaller number is the sum of distinct divisors of 1638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2184).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
1638 is a wasteful number, since it uses less digits than its factorization.
1638 is an evil number, because the sum of its binary digits is even.
The square root of 1638 is about 40.4722126897. The cubic root of 1638 is about 11.7879413344.
The spelling of 1638 in words is "one thousand, six hundred thirty-eight".