21012866 has 16 divisors (see below), whose sum is σ = 36758400. Its totient is φ = 9005220.

The previous prime is 21012851. The next prime is 21012877. The reversal of 21012866 is 66821012.

It is an unprimeable number.

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, 14630 + ... + 16001.

It is an arithmetic number, because the mean of its divisors is an integer number (2297400).

Almost surely, 2^21012866 is an apocalyptic number.

21012866 is a deficient number, since it is larger than the sum of its proper divisors (15745534).

21012866 is an equidigital number, since it uses as much as digits as its factorization.

21012866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30654 (or 30640 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 21012866 is about 4583.9792756949. The cubic root of 21012866 is about 275.9487494981.

Adding to 21012866 its reverse (66821012), we get a palindrome (87833878).

The spelling of 21012866 in words is "twenty-one million, twelve thousand, eight hundred sixty-six".