21043404 has 36 divisors (see below), whose sum is σ = 54329184. Its totient is φ = 6864672.

The previous prime is 21043391. The next prime is 21043409. The reversal of 21043404 is 40434012.

Added to its reverse (40434012) it gives a triangular number (61477416 = T₁₁₀₈₈).

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21043409) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4527 + ... + 7910.

It is an arithmetic number, because the mean of its divisors is an integer number (1509144).

Almost surely, 2^21043404 is an apocalyptic number.

It is an amenable number.

21043404 is an abundant number, since it is smaller than the sum of its proper divisors (33285780).

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

21043404 is a wasteful number, since it uses less digits than its factorization.

21043404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12494 (or 12489 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21043404 is about 4587.3090150981. The cubic root of 21043404 is about 276.0823635725.

Adding to 21043404 its reverse (40434012), we get a palindrome (61477416).

The spelling of 21043404 in words is "twenty-one million, forty-three thousand, four hundred four".