21660047 has 2 divisors, whose sum is σ = 21660048. Its totient is φ = 21660046.

The previous prime is 21660011. The next prime is 21660053. The reversal of 21660047 is 74006612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21660047 - 2²⁰ = 20611471 is a prime.

It is a Chen prime.

It is equal to p_1369052 and since 21660047 and 1369052 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 21659998 and 21660025.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21660007) 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, 10830023 + 10830024.

It is an arithmetic number, because the mean of its divisors is an integer number (10830024).

Almost surely, 2^21660047 is an apocalyptic number.

21660047 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660047 is an equidigital number, since it uses as much as digits as its factorization.

21660047 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 26.

The square root of 21660047 is about 4654.0355606720. The cubic root of 21660047 is about 278.7531592877.

Adding to 21660047 its reverse (74006612), we get a palindrome (95666659).

The spelling of 21660047 in words is "twenty-one million, six hundred sixty thousand, forty-seven".