21105700 has 72 divisors (see below), whose sum is σ = 57121344. Its totient is φ = 6576000.

The previous prime is 21105683. The next prime is 21105703. The reversal of 21105700 is 750112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6330 + ... + 9070.

It is an arithmetic number, because the mean of its divisors is an integer number (793352).

Almost surely, 2^21105700 is an apocalyptic number.

21105700 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 21105700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28560672).

21105700 is an abundant number, since it is smaller than the sum of its proper divisors (36015644).

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

21105700 is a wasteful number, since it uses less digits than its factorization.

21105700 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2773 (or 2766 counting only the distinct ones).

The product of its (nonzero) digits is 70, while the sum is 16.

The square root of 21105700 is about 4594.0940347363. The cubic root of 21105700 is about 276.3545293498.

Adding to 21105700 its reverse (750112), we get a palindrome (21855812).

The spelling of 21105700 in words is "twenty-one million, one hundred five thousand, seven hundred".