21256560 has 160 divisors (see below), whose sum is σ = 78953280. Its totient is φ = 5225472.

The previous prime is 21256559. The next prime is 21256567. The reversal of 21256560 is 6565212.

21256560 is a `hidden beast` number, since 2 + 1 + 2 + 5 + 656 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256567) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 27702 + ... + 28458.

It is an arithmetic number, because the mean of its divisors is an integer number (493458).

Almost surely, 2^21256560 is an apocalyptic number.

21256560 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 21256560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39476640).

21256560 is an abundant number, since it is smaller than the sum of its proper divisors (57696720).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21256560 is a wasteful number, since it uses less digits than its factorization.

21256560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 792 (or 780 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 21256560 is about 4610.4837056430. The cubic root of 21256560 is about 277.0114119901.

The spelling of 21256560 in words is "twenty-one million, two hundred fifty-six thousand, five hundred sixty".