21304447 has 2 divisors, whose sum is σ = 21304448. Its totient is φ = 21304446.

The previous prime is 21304441. The next prime is 21304457. The reversal of 21304447 is 74440312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21304447 - 2⁷ = 21304319 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21304441) 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 as a sum of consecutive naturals, namely, 10652223 + 10652224.

It is an arithmetic number, because the mean of its divisors is an integer number (10652224).

Almost surely, 2^21304447 is an apocalyptic number.

21304447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21304447 is an equidigital number, since it uses as much as digits as its factorization.

21304447 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 21304447 is about 4615.6740569499. The cubic root of 21304447 is about 277.2192740427.

Adding to 21304447 its reverse (74440312), we get a palindrome (95744759).

The spelling of 21304447 in words is "twenty-one million, three hundred four thousand, four hundred forty-seven".