21560 has 48 divisors (see below), whose sum is σ = 61560. Its totient is φ = 6720.

The previous prime is 21559. The next prime is 21563. The reversal of 21560 is 6512.

It is a Harshad number since it is a multiple of its sum of digits (14).

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.

It is not an unprimeable number, because it can be changed into a prime (21563) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1955 + ... + 1965.

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).

21560 is an abundant number, since it is smaller than the sum of its proper divisors (40000).

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 sum of its prime factors is 36 (or 25 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21560 is about 146.8332387438. The cubic root of 21560 is about 27.8323313092.

21560 divided by its sum of digits (14) gives a triangular number (1540 = T₅₅).

The spelling of 21560 in words is "twenty-one thousand, five hundred sixty".