21660011 has 2 divisors, whose sum is σ = 21660012. Its totient is φ = 21660010.

The previous prime is 21660007. The next prime is 21660047. The reversal of 21660011 is 11006612.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21660011 - 2² = 21660007 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21660211) 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, 10830005 + 10830006.

It is an arithmetic number, because the mean of its divisors is an integer number (10830006).

Almost surely, 2^21660011 is an apocalyptic number.

21660011 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660011 is an equidigital number, since it uses as much as digits as its factorization.

21660011 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 21660011 is about 4654.0316930593. The cubic root of 21660011 is about 278.7530048541.

Adding to 21660011 its reverse (11006612), we get a palindrome (32666623).

The spelling of 21660011 in words is "twenty-one million, six hundred sixty thousand, eleven".