21101800 has 24 divisors (see below), whose sum is σ = 49062150. Its totient is φ = 8440640.

The previous prime is 21101789. The next prime is 21101809. The reversal of 21101800 is 810112.

It can be written as a sum of positive squares in 3 ways, for example, as 17189316 + 3912484 = 4146^2 + 1978^2 .

It is not an unprimeable number, because it can be changed into a prime (21101809) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 52555 + ... + 52954.

Almost surely, 2^21101800 is an apocalyptic number.

21101800 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21101800 is an abundant number, since it is smaller than the sum of its proper divisors (27960350).

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

21101800 is a wasteful number, since it uses less digits than its factorization.

21101800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105525 (or 105516 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 21101800 is about 4593.6695571188. The cubic root of 21101800 is about 276.3375063172.

Adding to 21101800 its reverse (810112), we get a palindrome (21911912).

The spelling of 21101800 in words is "twenty-one million, one hundred one thousand, eight hundred".