21184421 has 4 divisors (see below), whose sum is σ = 21301644. Its totient is φ = 21067200.

The previous prime is 21184393. The next prime is 21184441. The reversal of 21184421 is 12448112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4456321 + 16728100 = 2111^2 + 4090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21184421 - 2¹⁸ = 20922277 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 (21184441) 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, 58340 + ... + 58701.

It is an arithmetic number, because the mean of its divisors is an integer number (5325411).

Almost surely, 2^21184421 is an apocalyptic number.

It is an amenable number.

21184421 is a deficient number, since it is larger than the sum of its proper divisors (117223).

21184421 is a wasteful number, since it uses less digits than its factorization.

21184421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117222.

The product of its digits is 512, while the sum is 23.

The square root of 21184421 is about 4602.6536910787. The cubic root of 21184421 is about 276.6976896230.

The spelling of 21184421 in words is "twenty-one million, one hundred eighty-four thousand, four hundred twenty-one".