21556434536 has 128 divisors (see below), whose sum is σ = 52605020160. Its totient is φ = 8051097600.

The previous prime is 21556434511. The next prime is 21556434583. The reversal of 21556434536 is 63543465512.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 913640 + ... + 936936.

It is an arithmetic number, because the mean of its divisors is an integer number (410976720).

Almost surely, 2^21556434536 is an apocalyptic number.

21556434536 is a gapful number since it is divisible by the number (26) 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 21556434536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26302510080).

21556434536 is an abundant number, since it is smaller than the sum of its proper divisors (31048585624).

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

21556434536 is a wasteful number, since it uses less digits than its factorization.

21556434536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23395 (or 23391 counting only the distinct ones).

The product of its digits is 1296000, while the sum is 44.

The spelling of 21556434536 in words is "twenty-one billion, five hundred fifty-six million, four hundred thirty-four thousand, five hundred thirty-six".