21043900 has 36 divisors (see below), whose sum is σ = 46052608. Its totient is φ = 8346240.

The previous prime is 21043871. The next prime is 21043901. The reversal of 21043900 is 934012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21043901) 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 11 ways as a sum of consecutive naturals, for example, 11872 + ... + 13528.

Almost surely, 2^21043900 is an apocalyptic number.

21043900 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 21043900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23026304).

21043900 is an abundant number, since it is smaller than the sum of its proper divisors (25008708).

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

21043900 is a wasteful number, since it uses less digits than its factorization.

21043900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1798 (or 1791 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 21043900 is about 4587.3630769757. The cubic root of 21043900 is about 276.0845326730.

Adding to 21043900 its reverse (934012), we get a palindrome (21977912).

The spelling of 21043900 in words is "twenty-one million, forty-three thousand, nine hundred".