21308047 has 2 divisors, whose sum is σ = 21308048. Its totient is φ = 21308046.

The previous prime is 21308029. The next prime is 21308057. The reversal of 21308047 is 74080312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21308047 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21308017) 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 as a sum of consecutive naturals, namely, 10654023 + 10654024.

It is an arithmetic number, because the mean of its divisors is an integer number (10654024).

Almost surely, 2^21308047 is an apocalyptic number.

21308047 is a deficient number, since it is larger than the sum of its proper divisors (1).

21308047 is an equidigital number, since it uses as much as digits as its factorization.

21308047 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21308047 is about 4616.0640160206. The cubic root of 21308047 is about 277.2348878905.

Adding to 21308047 its reverse (74080312), we get a palindrome (95388359).

The spelling of 21308047 in words is "twenty-one million, three hundred eight thousand, forty-seven".