21404221 has 8 divisors (see below), whose sum is σ = 21780000. Its totient is φ = 21031920.

The previous prime is 21404213. The next prime is 21404263. The reversal of 21404221 is 12240412.

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 21404221 - 2³ = 21404213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21404195 and 21404204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13530 + ... + 15028.

It is an arithmetic number, because the mean of its divisors is an integer number (2722500).

Almost surely, 2^21404221 is an apocalyptic number.

It is an amenable number.

21404221 is a deficient number, since it is larger than the sum of its proper divisors (375779).

21404221 is a wasteful number, since it uses less digits than its factorization.

21404221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1739.

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 21404221 is about 4626.4696043528. The cubic root of 21404221 is about 277.6513623828.

Adding to 21404221 its reverse (12240412), we get a palindrome (33644633).

The spelling of 21404221 in words is "twenty-one million, four hundred four thousand, two hundred twenty-one".