21100800 has 216 divisors, whose sum is σ = 80092096. Its totient is φ = 4792320.

The previous prime is 21100789. The next prime is 21100813. The reversal of 21100800 is 800112.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 134322 + ... + 134478.

Almost surely, 2^21100800 is an apocalyptic number.

21100800 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 21100800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40046048).

21100800 is an abundant number, since it is smaller than the sum of its proper divisors (58991296).

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

21100800 is a wasteful number, since it uses less digits than its factorization.

21100800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193 (or 174 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

The square root of 21100800 is about 4593.5607103858. The cubic root of 21100800 is about 276.3331410992. Note that the first 3 decimals are identical.

Adding to 21100800 its reverse (800112), we get a palindrome (21900912).

The spelling of 21100800 in words is "twenty-one million, one hundred thousand, eight hundred".