21128560 has 40 divisors (see below), whose sum is σ = 49595040. Its totient is φ = 8370432.

The previous prime is 21128543. The next prime is 21128561. The reversal of 21128560 is 6582112.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21128561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7509 + ... + 9931.

It is an arithmetic number, because the mean of its divisors is an integer number (1239876).

Almost surely, 2^21128560 is an apocalyptic number.

21128560 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 21128560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24797520).

21128560 is an abundant number, since it is smaller than the sum of its proper divisors (28466480).

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

21128560 is a wasteful number, since it uses less digits than its factorization.

21128560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2545 (or 2539 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21128560 is about 4596.5813383427. The cubic root of 21128560 is about 276.4542683627.

It can be divided in two parts, 21128 and 560, that multiplied together give a triangular number (11831680 = T₄₈₆₄).

The spelling of 21128560 in words is "twenty-one million, one hundred twenty-eight thousand, five hundred sixty".