21284447 has 4 divisors (see below), whose sum is σ = 21294720. Its totient is φ = 21274176.

The previous prime is 21284423. The next prime is 21284489. The reversal of 21284447 is 74448212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21284447 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 (21284947) 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 3 ways as a sum of consecutive naturals, for example, 818 + ... + 6575.

It is an arithmetic number, because the mean of its divisors is an integer number (5323680).

Almost surely, 2^21284447 is an apocalyptic number.

21284447 is a deficient number, since it is larger than the sum of its proper divisors (10273).

21284447 is an equidigital number, since it uses as much as digits as its factorization.

21284447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10272.

The product of its digits is 14336, while the sum is 32.

The square root of 21284447 is about 4613.5070174435. The cubic root of 21284447 is about 277.1324983982.

The spelling of 21284447 in words is "twenty-one million, two hundred eighty-four thousand, four hundred forty-seven".