21200400 has 240 divisors, whose sum is σ = 81800320. Its totient is φ = 5184000.

The previous prime is 21200383. The next prime is 21200401. The reversal of 21200400 is 400212.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is not an unprimeable number, because it can be changed into a prime (21200401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 140325 + ... + 140475.

Almost surely, 2^21200400 is an apocalyptic number.

21200400 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 21200400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40900160).

21200400 is an abundant number, since it is smaller than the sum of its proper divisors (60599920).

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

21200400 is a wasteful number, since it uses less digits than its factorization.

21200400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191 (or 174 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

The square root of 21200400 is about 4604.3892103079. The cubic root of 21200400 is about 276.7672413815.

Adding to 21200400 its reverse (400212), we get a palindrome (21600612).

The spelling of 21200400 in words is "twenty-one million, two hundred thousand, four hundred".