21021866 has 8 divisors (see below), whose sum is σ = 33192480. Its totient is φ = 9957708.

The previous prime is 21021863. The next prime is 21021887. The reversal of 21021866 is 66812012.

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

It is not an unprimeable number, because it can be changed into a prime (21021863) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 276566 + ... + 276641.

It is an arithmetic number, because the mean of its divisors is an integer number (4149060).

Almost surely, 2^21021866 is an apocalyptic number.

21021866 is a deficient number, since it is larger than the sum of its proper divisors (12170614).

21021866 is a wasteful number, since it uses less digits than its factorization.

21021866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553228.

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

The square root of 21021866 is about 4584.9608504326. The cubic root of 21021866 is about 275.9881409873.

Adding to 21021866 its reverse (66812012), we get a palindrome (87833878).

The spelling of 21021866 in words is "twenty-one million, twenty-one thousand, eight hundred sixty-six".