21712 is nontrivially palindromic in base 10.
It is a plaindrome in base 15.
It is a zygodrome in base 15.
It is a congruent number.
21712 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
221712 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 21712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22320).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21712 is a wasteful number, since it uses less digits than its factorization.
21712 is an evil number, because the sum of its binary digits is even.
The square root of 21712 is about 147.3499236512. The cubic root of 21712 is about 27.8975850395.
The spelling of 21712 in words is "twenty-one thousand, seven hundred twelve", and thus it is an iban number.