21559051520 has 72 divisors (see below), whose sum is σ = 51842393064. Its totient is φ = 8589934592.

The previous prime is 21559051487. The next prime is 21559051561. The reversal of 21559051520 is 2515095512.

It can be written as a sum of positive squares in 4 ways, for example, as 16049849344 + 5509202176 = 126688^2 + 74224^2 .

It is a zygodrome in base 4.

It is a congruent number.

It is an unprimeable number.

In principle, a polygon with 21559051520 sides can be constructed with ruler and compass.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 296192 + ... + 361728.

It is an arithmetic number, because the mean of its divisors is an integer number (720033237).

Almost surely, 2^21559051520 is an apocalyptic number.

21559051520 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 21559051520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25921196532).

21559051520 is an abundant number, since it is smaller than the sum of its proper divisors (30283341544).

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

21559051520 is an equidigital number, since it uses as much as digits as its factorization.

21559051520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65815 (or 65801 counting only the distinct ones).

The product of its (nonzero) digits is 22500, while the sum is 35.

The spelling of 21559051520 in words is "twenty-one billion, five hundred fifty-nine million, fifty-one thousand, five hundred twenty".