21091200 has 192 divisors, whose sum is σ = 75255600. Its totient is φ = 5191680.

The previous prime is 21091193. The next prime is 21091201. The reversal of 21091200 is 219012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21091200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21091201) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1622394 + ... + 1622406.

Almost surely, 2^21091200 is an apocalyptic number.

21091200 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 21091200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37627800).

21091200 is an abundant number, since it is smaller than the sum of its proper divisors (54164400).

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

21091200 is an equidigital number, since it uses as much as digits as its factorization.

21091200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66 (or 23 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 15.

The square root of 21091200 is about 4592.5156504905. The cubic root of 21091200 is about 276.2912279875.

The spelling of 21091200 in words is "twenty-one million, ninety-one thousand, two hundred".