21778216520 has 64 divisors (see below), whose sum is σ = 51986156400. Its totient is φ = 8182620160.

The previous prime is 21778216519. The next prime is 21778216543. The reversal of 21778216520 is 2561287712.

It can be written as a sum of positive squares in 8 ways, for example, as 16910921764 + 4867294756 = 130042^2 + 69766^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 314660 + ... + 377580.

Almost surely, 2^21778216520 is an apocalyptic number.

21778216520 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 21778216520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25993078200).

21778216520 is an abundant number, since it is smaller than the sum of its proper divisors (30207939880).

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

21778216520 is a wasteful number, since it uses less digits than its factorization.

21778216520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63458 (or 63454 counting only the distinct ones).

The product of its (nonzero) digits is 94080, while the sum is 41.

The spelling of 21778216520 in words is "twenty-one billion, seven hundred seventy-eight million, two hundred sixteen thousand, five hundred twenty".