21006866 has 16 divisors (see below), whose sum is σ = 34815744. Its totient is φ = 9455424.

The previous prime is 21006863. The next prime is 21006877. The reversal of 21006866 is 66860012.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21006863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12650 + ... + 14213.

It is an arithmetic number, because the mean of its divisors is an integer number (2175984).

Almost surely, 2^21006866 is an apocalyptic number.

21006866 is a deficient number, since it is larger than the sum of its proper divisors (13808878).

21006866 is a wasteful number, since it uses less digits than its factorization.

21006866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26905.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21006866 is about 4583.3247757496. The cubic root of 21006866 is about 275.9224822561.

Adding to 21006866 its reverse (66860012), we get a palindrome (87866878).

The spelling of 21006866 in words is "twenty-one million, six thousand, eight hundred sixty-six".