21043405 has 8 divisors (see below), whose sum is σ = 25556832. Its totient is φ = 16631568.

The previous prime is 21043391. The next prime is 21043409. The reversal of 21043405 is 50434012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21043405 - 2¹¹ = 21041357 is a prime.

It is a Duffinian number.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 24939 + ... + 25768.

It is an arithmetic number, because the mean of its divisors is an integer number (3194604).

Almost surely, 2^21043405 is an apocalyptic number.

It is an amenable number.

21043405 is a deficient number, since it is larger than the sum of its proper divisors (4513427).

21043405 is an equidigital number, since it uses as much as digits as its factorization.

21043405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50795.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21043405 is about 4587.3091240944. The cubic root of 21043405 is about 276.0823679457.

Adding to 21043405 its reverse (50434012), we get a palindrome (71477417).

The spelling of 21043405 in words is "twenty-one million, forty-three thousand, four hundred five".