21808866 has 8 divisors (see below), whose sum is σ = 43617744. Its totient is φ = 7269620.

The previous prime is 21808861. The next prime is 21808867. The reversal of 21808866 is 66880812.

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

21808866 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21808861) 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, 1817400 + ... + 1817411.

It is an arithmetic number, because the mean of its divisors is an integer number (5452218).

Almost surely, 2^21808866 is an apocalyptic number.

21808866 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21808866 is a wasteful number, since it uses less digits than its factorization.

21808866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3634816.

The product of its (nonzero) digits is 36864, while the sum is 39.

The square root of 21808866 is about 4669.9963597416. The cubic root of 21808866 is about 279.3901095882.

The spelling of 21808866 in words is "twenty-one million, eight hundred eight thousand, eight hundred sixty-six".