21211505520 has 80 divisors (see below), whose sum is σ = 66086246400. Its totient is φ = 5627964672.

The previous prime is 21211505509. The next prime is 21211505527. The reversal of 21211505520 is 2550511212.

It is a tau number, because it is divible by the number of its divisors (80).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211505527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 174304 + ... + 269823.

It is an arithmetic number, because the mean of its divisors is an integer number (826078080).

Almost surely, 2^21211505520 is an apocalyptic number.

21211505520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21211505520 is an abundant number, since it is smaller than the sum of its proper divisors (44874740880).

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

21211505520 is a wasteful number, since it uses less digits than its factorization.

21211505520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444342 (or 444336 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 24.

The spelling of 21211505520 in words is "twenty-one billion, two hundred eleven million, five hundred five thousand, five hundred twenty".