21521760 has 96 divisors (see below), whose sum is σ = 73029600. Its totient is φ = 5296128.

The previous prime is 21521743. The next prime is 21521771. The reversal of 21521760 is 6712512.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a zygodrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 21521760.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4516 + ... + 7964.

It is an arithmetic number, because the mean of its divisors is an integer number (760725).

Almost surely, 2^21521760 is an apocalyptic number.

21521760 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 21521760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36514800).

21521760 is an abundant number, since it is smaller than the sum of its proper divisors (51507840).

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

21521760 is a wasteful number, since it uses less digits than its factorization.

21521760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3480 (or 3472 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21521760 is about 4639.1550954888. The cubic root of 21521760 is about 278.1586658738.

The spelling of 21521760 in words is "twenty-one million, five hundred twenty-one thousand, seven hundred sixty".