21560 divided by its sum of digits (14) gives a triangular number (1540 = T55).
It is an Ulam number.
It is a zygodrome in base 7.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21560.
221560 is an apocalyptic number.
21560 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 21560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30780).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21560 is a wasteful number, since it uses less digits than its factorization.
21560 is an evil number, because the sum of its binary digits is even.
The square root of 21560 is about 146.8332387438. The cubic root of 21560 is about 27.8323313092.
The spelling of 21560 in words is "twenty-one thousand, five hundred sixty".