21055434400 has 288 divisors, whose sum is σ = 69017332608. Its totient is φ = 6057676800.

The previous prime is 21055434373. The next prime is 21055434401. The reversal of 21055434400 is 443455012.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is not an unprimeable number, because it can be changed into a prime (21055434401) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 787654 + ... + 813946.

It is an arithmetic number, because the mean of its divisors is an integer number (239643516).

Almost surely, 2^21055434400 is an apocalyptic number.

21055434400 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 21055434400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34508666304).

21055434400 is an abundant number, since it is smaller than the sum of its proper divisors (47961898208).

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

21055434400 is a wasteful number, since it uses less digits than its factorization.

21055434400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26344 (or 26331 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 28.

Adding to 21055434400 its reverse (443455012), we get a palindrome (21498889412).

The spelling of 21055434400 in words is "twenty-one billion, fifty-five million, four hundred thirty-four thousand, four hundred".