21043236 has 12 divisors (see below), whose sum is σ = 49100912. Its totient is φ = 7014408.

The previous prime is 21043223. The next prime is 21043237. The reversal of 21043236 is 63234012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21043237) 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 3 ways as a sum of consecutive naturals, for example, 876790 + ... + 876813.

Almost surely, 2^21043236 is an apocalyptic number.

It is an amenable number.

21043236 is an abundant number, since it is smaller than the sum of its proper divisors (28057676).

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

21043236 is a wasteful number, since it uses less digits than its factorization.

21043236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1753610 (or 1753608 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 21.

The square root of 21043236 is about 4587.2907036725. The cubic root of 21043236 is about 276.0816288694.

Adding to 21043236 its reverse (63234012), we get a palindrome (84277248).

The spelling of 21043236 in words is "twenty-one million, forty-three thousand, two hundred thirty-six".