It is a plaindrome in base 15.
221700 is an apocalyptic number.
21700 is a gapful number since it is divisible by the number (20) 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 21700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27776).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21700 is a wasteful number, since it uses less digits than its factorization.
21700 is an evil number, because the sum of its binary digits is even.
The square root of 21700 is about 147.3091986266. The cubic root of 21700 is about 27.8924445226.
The spelling of 21700 in words is "twenty-one thousand, seven hundred", and thus it is an iban number.