21004421 has 4 divisors (see below), whose sum is σ = 21200832. Its totient is φ = 20808012.

The previous prime is 21004387. The next prime is 21004447. The reversal of 21004421 is 12440012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21004421 - 2¹⁰ = 21003397 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21004396 and 21004405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21004471) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 98045 + ... + 98258.

It is an arithmetic number, because the mean of its divisors is an integer number (5300208).

Almost surely, 2^21004421 is an apocalyptic number.

It is an amenable number.

21004421 is a deficient number, since it is larger than the sum of its proper divisors (196411).

21004421 is a wasteful number, since it uses less digits than its factorization.

21004421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196410.

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21004421 is about 4583.0580402173. The cubic root of 21004421 is about 275.9117769206.

Adding to 21004421 its reverse (12440012), we get a palindrome (33444433).

The spelling of 21004421 in words is "twenty-one million, four thousand, four hundred twenty-one".