21404009 has 8 divisors (see below), whose sum is σ = 23919840. Its totient is φ = 18983200.

The previous prime is 21403979. The next prime is 21404017. The reversal of 21404009 is 90040412.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21404009 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21404029) 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, 23279 + ... + 24180.

It is an arithmetic number, because the mean of its divisors is an integer number (2989980).

Almost surely, 2^21404009 is an apocalyptic number.

It is an amenable number.

21404009 is a deficient number, since it is larger than the sum of its proper divisors (2515831).

21404009 is a wasteful number, since it uses less digits than its factorization.

21404009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47511.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21404009 is about 4626.4466926573. The cubic root of 21404009 is about 277.6504457057.

The spelling of 21404009 in words is "twenty-one million, four hundred four thousand, nine".