21559406400 has 504 divisors, whose sum is σ = 92191311680. Its totient is φ = 4668088320.

The previous prime is 21559406399. The next prime is 21559406459. The reversal of 21559406400 is 460495512.

21559406400 is a `hidden beast` number, since 2 + 1 + 5 + 5 + 9 + 4 + 0 + 640 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (504).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

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 71 ways as a sum of consecutive naturals, for example, 1909572 + ... + 1920828.

Almost surely, 2^21559406400 is an apocalyptic number.

21559406400 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 21559406400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46095655840).

21559406400 is an abundant number, since it is smaller than the sum of its proper divisors (70631905280).

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

21559406400 is a wasteful number, since it uses less digits than its factorization.

21559406400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11311 (or 11293 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

The spelling of 21559406400 in words is "twenty-one billion, five hundred fifty-nine million, four hundred six thousand, four hundred".