21855385520 has 40 divisors (see below), whose sum is σ = 50821367760. Its totient is φ = 8740847360.

The previous prime is 21855385463. The next prime is 21855385529. The reversal of 21855385520 is 2558355812.

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

It is a super-3 number, since 3×21855385520³ (a number of 32 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21855385529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 658115 + ... + 690525.

It is an arithmetic number, because the mean of its divisors is an integer number (1270534194).

Almost surely, 2^21855385520 is an apocalyptic number.

21855385520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21855385520 is an abundant number, since it is smaller than the sum of its proper divisors (28965982240).

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

21855385520 is a wasteful number, since it uses less digits than its factorization.

21855385520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40853 (or 40847 counting only the distinct ones).

The product of its (nonzero) digits is 480000, while the sum is 44.

The spelling of 21855385520 in words is "twenty-one billion, eight hundred fifty-five million, three hundred eighty-five thousand, five hundred twenty".