21504047 has 2 divisors, whose sum is σ = 21504048. Its totient is φ = 21504046.

The previous prime is 21504023. The next prime is 21504053. The reversal of 21504047 is 74040512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21504047 - 2⁸ = 21503791 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21504017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752023 + 10752024.

It is an arithmetic number, because the mean of its divisors is an integer number (10752024).

Almost surely, 2^21504047 is an apocalyptic number.

21504047 is a deficient number, since it is larger than the sum of its proper divisors (1).

21504047 is an equidigital number, since it uses as much as digits as its factorization.

21504047 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21504047 is about 4637.2456264468. The cubic root of 21504047 is about 278.0823341866.

Adding to 21504047 its reverse (74040512), we get a palindrome (95544559).

The spelling of 21504047 in words is "twenty-one million, five hundred four thousand, forty-seven".