21543555320 has 128 divisors (see below), whose sum is σ = 58767897600. Its totient is φ = 6938658816.

The previous prime is 21543555311. The next prime is 21543555323. The reversal of 21543555320 is 2355534512.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21543555323) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2675861 + ... + 2683899.

It is an arithmetic number, because the mean of its divisors is an integer number (459124200).

Almost surely, 2^21543555320 is an apocalyptic number.

21543555320 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 21543555320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29383948800).

21543555320 is an abundant number, since it is smaller than the sum of its proper divisors (37224342280).

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

21543555320 is a wasteful number, since it uses less digits than its factorization.

21543555320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8637 (or 8633 counting only the distinct ones).

The product of its (nonzero) digits is 90000, while the sum is 35.

The spelling of 21543555320 in words is "twenty-one billion, five hundred forty-three million, five hundred fifty-five thousand, three hundred twenty".