21238447 has 4 divisors (see below), whose sum is σ = 22356280. Its totient is φ = 20120616.

The previous prime is 21238433. The next prime is 21238471. The reversal of 21238447 is 74483212.

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

It is a cyclic number.

It is not a de Polignac number, because 21238447 - 2¹¹ = 21236399 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 (21238487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 558888 + ... + 558925.

It is an arithmetic number, because the mean of its divisors is an integer number (5589070).

Almost surely, 2^21238447 is an apocalyptic number.

21238447 is a deficient number, since it is larger than the sum of its proper divisors (1117833).

21238447 is a wasteful number, since it uses less digits than its factorization.

21238447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1117832.

The product of its digits is 10752, while the sum is 31.

The square root of 21238447 is about 4608.5189594923. The cubic root of 21238447 is about 276.9327079173.

The spelling of 21238447 in words is "twenty-one million, two hundred thirty-eight thousand, four hundred forty-seven".