21585680 has 40 divisors (see below), whose sum is σ = 51418584. Its totient is φ = 8422400.

The previous prime is 21585677. The next prime is 21585713. The reversal of 21585680 is 8658512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 204304 + 21381376 = 452^2 + 4624^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a self number, because there is not a number n which added to its sum of digits gives 21585680.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11 + ... + 6570.

Almost surely, 2^21585680 is an apocalyptic number.

21585680 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 21585680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25709292).

21585680 is an abundant number, since it is smaller than the sum of its proper divisors (29832904).

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

21585680 is a wasteful number, since it uses less digits than its factorization.

21585680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6635 (or 6629 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 35.

The square root of 21585680 is about 4646.0391733174. The cubic root of 21585680 is about 278.4337723816.

The spelling of 21585680 in words is "twenty-one million, five hundred eighty-five thousand, six hundred eighty".