21011866 has 8 divisors (see below), whose sum is σ = 31587264. Its totient is φ = 10482780.

The previous prime is 21011843. The next prime is 21011869. The reversal of 21011866 is 66811012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21011866.

It is not an unprimeable number, because it can be changed into a prime (21011869) 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 in 3 ways as a sum of consecutive naturals, for example, 10420 + ... + 12271.

It is an arithmetic number, because the mean of its divisors is an integer number (3948408).

Almost surely, 2^21011866 is an apocalyptic number.

21011866 is a deficient number, since it is larger than the sum of its proper divisors (10575398).

21011866 is a wasteful number, since it uses less digits than its factorization.

21011866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23156.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21011866 is about 4583.8701988603. The cubic root of 21011866 is about 275.9443719717.

Adding to 21011866 its reverse (66811012), we get a palindrome (87822878).

The spelling of 21011866 in words is "twenty-one million, eleven thousand, eight hundred sixty-six".