It is a tau number, because it is divible by the number of its divisors (96).
It is a nude number because it is divisible by every one of its digits.
It is a nialpdrome in base 6 and base 12.
It is a zygodrome in base 6.
217728 is a Friedman number, since it can be written as (12^(7-2)*7)/8, using all its digits and the basic arithmetic operations.
2217728 is an apocalyptic number.
217728 is a gapful number since it is divisible by the number (28) formed by its first and last digit.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 217728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (371280).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
217728 is an frugal number, since it uses more digits than its factorization.
217728 is an evil number, because the sum of its binary digits is even.
The square root of 217728 is about 466.6133302854. The cubic root of 217728 is about 60.1595752196.
The spelling of 217728 in words is "two hundred seventeen thousand, seven hundred twenty-eight".