21668111 has 2 divisors, whose sum is σ = 21668112. Its totient is φ = 21668110.

The previous prime is 21668107. The next prime is 21668123. The reversal of 21668111 is 11186612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21668111 - 2² = 21668107 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21668161) 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, 10834055 + 10834056.

It is an arithmetic number, because the mean of its divisors is an integer number (10834056).

Almost surely, 2^21668111 is an apocalyptic number.

21668111 is a deficient number, since it is larger than the sum of its proper divisors (1).

21668111 is an equidigital number, since it uses as much as digits as its factorization.

21668111 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576, while the sum is 26.

The square root of 21668111 is about 4654.9018249583. The cubic root of 21668111 is about 278.7877481104.

The spelling of 21668111 in words is "twenty-one million, six hundred sixty-eight thousand, one hundred eleven".